Here is a pretty good primer on engine oil and some suggestions on how to determine what is the best oil to use in your turbo Dodge. I put this together because oils have changed in 25+ years and there is a lot of confusion over the grading systems, the additives that were but are no more, viscosity, API ratings, etc. I've tried to start at the beginning and not assume much of anything with regard to what we all do or don't know about the current selections of engine oil products. What I've attempted to do is start w/the basics and then build a knowledge base of facts leading up to some suggestions at the conclusion.

I hope this in some way help you determine what will truly be the best oil for your intended application.

***** The Hitch Hikers Guide to the Galaxy of Engine Oils *****

How much do you value the engine in your car? The life of your engine depends in no small part on the quality of the oil you put in it - oil is its lifeblood. People typically don't pay much attention to their oil - oil is oil, right? In the bad old days, maybe, but engine oil underwent something of a revolution in the 80's and 90's when hot hatches, 16-valve engines and turbos started to become popular. Combined with the devastating problems of black death the days of one oil catering for everyone are over. Those days are GONE!

Take Castrol for example. They led the field for years with their GTX mineral oil. This was eventually surpassed by semi-synthetic and fully synthetic oils, including GTX2 and GTX3 Lightec. Those were surpassed by Formula SLX and most recently, Castrol GTX Magnatec. All manufacturers have a similar broad spectrum of oils now - I just mention Castrol in particular as they WERE my oil of choice for my own cars....back when I was a teenager and through my 20's and early 30s. That was when I bought my first turbo Dodge, 1984.

What does my oil actually do?

Your engine oil performs many functions. It stops all the metal surfaces in your engine from grinding together and tearing themselves apart from friction, and it transfers heat away from the combustion cycle. Engine oil must also be able to hold in suspension all the nasty by-products of combustion like silica (silicon oxide) and acids. Finally, engine oil minimizes the exposure to oxygen and thus oxidation at higher temperatures. It does all of these things under tremendous heat and pressure.

How do I read the numbers around the 'W'? For example 5W40?

As oils heat up, they generally get thinner. Single grade oils get too thin when hot for most modern engines which is where multigrade oil comes in. The idea is simple - use science and physics to prevent the base oil from getting too thin when it gets hot. The number before the 'W' is the 'cold' viscosity rating of the oil, and the number after the 'W' is the 'hot' viscosity rating. So a 5W40 oil is one that behaves like a 5-rated single grade oil when cold, but doesn't thin any more than a 40-rated single grade oil when hot. The lower the 'winter' number (hence the 'W'), the easier the engine will turn over when starting in cold climates. There's more detail on this later in the page under both viscosity, and SAE ratings.

A quick guide to the different grades of oil.

What the heck was Black Death?

Black Death first appeared in the early 80's when a sticky black substance was found to be the cause of many engine seizures in Europe. It was extremely frustrating for vehicle owners because dealers and mechanics had no idea what was going on. Black Death just wasn't covered under insurance - if your engine had it, you paid to fix it yourself. Many engines were affected but Ford and Vauxhall (GM) suffered the most. Faster roads, higher under-hood temperatures, tighter engineering tolerances and overworked engine oils turned out to be contributors to the problem. The oils just couldn't handle it and changed their chemical makeup under pressure into a sort of tar-like glue. This blocked all the oil channels in the engines, starved them of lubrication and caused them to seize. I don't recommend this but you can reproduce the effect with a frying pan, cooking oil and a blowtorch. The cooking oil will heat up far quicker than it's designed to and will turn to a sticky black tar in your pan. Either that or it will set fire to your kitchen, which is why I said "don't do this".

Anyway, burning kitchens aside, Black Death was the catalyst for the production of newer higher quality oils, many of them man-made rather than mineral-based.

Black death for the 21st century

There's a snappy new moniker for Black Death now: sludge. The cause is the same as Black Death and it seems to be regardless of maintenance or mileage. The chemical compounds in engine oils break down over time due to prolonged exposure to high temperatures and poor maintenance habits. When the oil oxidises, the additives separate from it and begin to chemically break down and solidify, leading to the baked-on oil deposits turning gelatinous, like black yoghurt. What doesn't help is that due to packaging, modern engines have smaller sumps than their older counterparts, and so hold less oil. This lower volume of oil can't hold as much crap (for want of a better word) and that can lead to earlier chemical breakdown.

The most common factor in sludge buildup is a combination of mineral oils, a lack of maintenance by the car owner and harsh driving conditions. However, a 2005 Consumer Reports article discovered that some engines from Audi, Chrysler, Saab, Toyota, and Volkswagen appear prone to sludge almost no matter how often the oil is changed.
What does sludge look like?

I was contacted by a BMW driver who had been having a particularly harsh time with sludge and was discussing it on the Bimmerfest forums. He posted some images of his problem and other readers posted similarly-framed images of the same engine components in "normal" condition. Here are two of those photos. On the top is what the cam case should look like in a well maintained engine when photographed through the oil filler cap. On the bottom is what the same type of engine looks like when suffering sludge buildup.

In this example, the consensus was that the sludge buildup was caused by an overheating engine, oil that hadn't been changed for 20,000 miles of stop-go city driving, a lot of cold starts and a period of about 12 months in storage without an oil change.

Curing sludge

There are no hard and fast rules for curing an engine of sludge buildup. If it's really bad, flushing the engine might be the only cure, but that could also cause even more problems. If flushing the engine results in bits of sludge getting lodged where they can do more damage, you're actually worse off.

It's interesting to note that some race techs have reported sludge buildup in race engines as a result of aftermarket additives being used in conjunction with the regular oil. The chemical composition of the additives isn't as neutral as some companies would lead us to believe, and combined with particular types of oil and high-stress driving, they can cause oil breakdown and sludge to appear. The lesson from them appears to be "don't use additives".

When is sludge not sludge?

Easy; when it's an oil and water emulsion from a leaking or blown head gasket. If this happens, you get a whitish cream colored sludge on the inside of the oil filler cap that looks like vanilla yogurt or mayonnaise. The cap is typically cooler than the rest of the cam case and so the oil/water mix tends to condense there. If the underside of your filler cap has this sort of deposit on it, chances are the engine has a blown head gasket. A surefire way to confirm this is if your oil level is going up and your coolant level is going down. The coolant gets through the breaks in the head gasket and mixes with the oil. When it gets to the sump it separates out and the oil floats on top. A more accurate way to check for this condition is to use a combustion leak tester, or block tester. If you're in America, NAPA sell them for about $45 (part #BK 7001006). If you're in England, Sealey sell them for about £70 (model number VS0061). Combustion leak testers are basically a turkey baster filled with PH liquid, with a non-return valve at the bottom. To use one, run your engine for a few minutes until its warm (not hot) then turn it off. Use a protective glove (like an oven glove) and take the radiator or reservoir cap off. Plug the bottom of the combustion leak tester into the hole and squeeze the rubber bulb on top. It will suck air from the top of the coolant through the non-return valve and bubble it through the PH liquid. If the liquid changes colour (normally blue to yellow), it means there is combustion gas in the coolant which means a head gasket leak.

Note: There is one other possible cause for the mayonnaise: a blocked scavenger hose. Most engines have a hose that comes off the cam cover and returns to the engine block somewhere via a vacuum line. This is the scavenger hose that scavenges oil vapor and gasses that build up in the cam cover. If it's blocked you can end up with a buildup of condensation inside the cam cover, which can manifest itself as the yellow goop inside the filler cap.

Mineral or synthetic motor oil?

Mineral oils are based on oil that comes from dear old Mother Earth which has been refined. Synthetic oils are mostly concocted by chemists wearing white lab coats in oil company laboratories. The only other type is semi-synthetic, sometimes called premium, which is a blend of the two. It is safe to mix the different types, but it's wiser to switch completely to a new type rather than mixing.


Despite their name, most synthetic derived motor oils (ie Mobil 1, Castrol Formula RS etc) are actually derived from mineral oils - they are mostly Polyalphaolifins and these come from the purest part of the mineral oil refraction process, the gas. PAO oils will mix with normal mineral oils which means you can add synthetic to mineral, or mineral to synthetic without your engine seizing up (although I've heard Mobil 1 is actually made by reformulating ethanol).

These bases are pretty stable, and by stable I mean 'less likely to react adversely with other compounds' because they tend not to contain reactive carbon atoms. Reactive carbon has a tendency to combine with oxygen creating an acid. (As you can imagine, in an oil this would be A Bad Thing.) They also have high viscosity indices and high temperature oxidative stability. Typically a small amount of diester synthetic (a compound containing two ester groups) is added to counteract seal swell too. These diesters act as a detergent and will attack carbon residuals. So think of synthetic oils as custom-built oils. They're designed to do the job efficiently but without any of the excess baggage that can accompany mineral based oils.

Pure synthetics

Pure synthetic oils (polyalkyleneglycol) are the types used almost exclusively within the industrial sector in polyglycol oils for heavily loaded gearboxes. These are typically concocted by even more intelligent blokes in even whiter lab coats. These chaps break apart the molecules that make up a variety of substances, like vegetable and animal oils, and then recombine the individual atoms that make up those molecules to build new, synthetic molecules. This process allows the chemists to actually "fine tune" the molecules as they build them. Clever stuff. But Polyglycols don't mix with normal mineral oils.

[amsoil] While we're on synthetic oils, I should mention Amsoil. They contacted me and asked to point out the following:

Amsoil do NOT produce or market oil additives and do not wish to be associated with oil additives. They are a formulator of synthetic lubricants for automotive and industrial applications and have been in business for 30+ years. They are not a half-hour infomercial or fly-by-night product, nor have they ever been involved in a legal suit regarding their product claims in that 30+ year span. Many Amsoil products are API certified, and ALL of our products meet and in most cases exceed the specifications of ILSAC, AGMA etc. Their lubricants also exceed manufacturers specifications and Amsoil are on many manufacturers approval lists. They base their claims on ASTM certified tests and are very open to anyone, with nothing to hide.

Amsoil recommend engine oil additives are NOT to be used with their products. They have a pretty good FAQ on the Amsoil website: Amsoil FAQ (external link). There is also a particularly good page talking about testing Amsoil in taxis.

If I put new, fully synthetic oil in my older engine, will the seals leak?

This question comes up a lot from people who've just bought a used vehicle and are wanting to start their history with the car on fresh oil.

The short answer: generally speaking, not any more. The caveat is that your engine must be in good working order and not be leaking right now. If that's the case, most modern oils are fully compatible with the elastomeric materials that engine seals are made from, and you shouldn't have any issues with leaks.
The longer answer:

Mixing Mineral and Synthetic oils - current thinking

Here's the current thinking on the subject of mixing mineral and synthetic oils. This information is based on the answer to a technical question posed on the Shell Oil website:

There is no scientific data to support the idea that mixing mineral and synthetic oils will damage your engine. When switching from a mineral oil to a synthetic, or vice versa, you will potentially leave a small amount of residual oil in the engine. That's perfectly okay because synthetic oil and mineral-based motor oil are, for the most part, compatible with each other. (The exception is pure synthetics. Polyglycols don't mix with normal mineral oils.)
There is also no problem with switching back and forth between synthetic and mineral based oils. In fact, people who are "in the know" and who operate engines in areas where temperature fluctuations can be especially extreme, switch from mineral oil to synthetic oil for the colder months. They then switch back to mineral oil during the warmer months.

There was a time, years ago, when switching between synthetic oils and mineral oils was not recommended if you had used one product or the other for a long period of time. People experienced problems with seals leaking and high oil consumption but changes in additive chemistry and seal material have taken care of those issues. And that's an important caveat. New seal technology is great, but if you're still driving around in a car from the 80's with its original seals, then this argument becomes a bit of a moot point - your seals are still going to be subject to the old leakage problems no matter what newfangled additives the oil companies are putting in their products.

Flushing oils

These are special compound oils that are very, very thin. They almost have the consistency of tap water both when cold and hot. Typically they are 0W/20 oils. Their purpose is for cleaning out all the gunk which builds up inside an engine.

Note: Some hybrid vehicles now require 0W20, so if you're a hybrid driver, check your owner's manual. Also I believe Honda switched to recommending 0W20 in 2011 to meet their CAFE ratings (thinner oil gives less drag on engine parts which improves - fractionally - the mpg). If you look at 2010 models vs 2011, you'll see things like the Element and CR-V getting a tiny mpg boost in the official figures despite being the exact same car. They achieved this by remapping the gearbox shift points and dropping the cold viscosity rating on the oil. In reality unless you live in northern Alaska, or do an above average number of cold-start short journeys, 5W20 ought to be more than suitable.

Do I need a flushing oil?

Unless there's something seriously wrong with your engine, like you've filled it with milk or shampoo, you really ought never to need a flushing oil. If you do decide to do an oil flush, there's two ways of doing it. You can either use a dedicated flushing oil, or a flushing additive in your existing oil. Either way it's wise to change the filter first so you have a clean one to collect all the gunk. (This typically means draining the oil or working fast). Once you have a new filter in place, and the flushing oil (or flushing solution) in there, run the engine at a fast idle for about 20 minutes. Finally, drain all this off (and marvel at the crap that comes out with it), replace the oil filter again, refill with a good synthetic oil and voila! Clean(er) engine. For the curious among you, looking in the oil filter that was attached when you did the flush will be an educational exercise in the sort of debris that used to be in your engine.

Of course, like most things nowadays, there's a condition attached when using flushing oils. In an old engine you really don't want to remove all the deposits. Some of these deposits help seal rings, lifters and even some of the flanges between the heads, covers, pan and the block, where the gaskets are thin. I have heard of engines with over 280,000km that worked fine, but when flushed, failed in a month because the blow-by past the scraper ring (now really clean) contaminated the oil and ruined the rod bearings.

Using Diesel oil for flushing

A question came up some time ago about using diesel-rated oils to flush out petrol engines. The idea was that because of the higher detergent levels in diesel engine oil, it might be a good cleaner / flusher for a non-diesel engine. Well most of the diesel oil specification oils can be used in old petrol engines for cleaning, but you want to use a low specification oil to ensure that you do not over clean your engine and lose compression (for example). Generally speaking, an SAE 15W/40 diesel engine oil for about 500 miles might do the trick.

Which oil should you buy? (the short version)

That all depends on your car, your pocket and how you intend to drive and service the car. All brands claim theirs offers the best protection available - until they launch a superior alternative. It's like washing powders - whiter than white until new Super-Nukem-Dazzo comes out. For most motorists and most cars, a quality mainstream oil is the best, like Castrol GTX. Moving up a step, you could look at Duckhams QXR and Castrol Protection Plus and GTX3 Lightec. The latter two of these are designed specifically for engines with catalytic converters. They're also a good choice for GTi's and turbo engines. Go up a step again and you're looking at synthetic oils aimed squarely at the performance market like Mobil-1.

To help you through the maze of oils available, there's a site available now (the motor oil evaluator) that aims to lessen the confusion with a relatively balanced scoring system based on published specifications such as viscosity and pour point. It's a good starting point if you're looking for even more in-depth info.

Which oil should you buy? (the long version)

Quality Counts! It doesn't matter what sort of fancy marketing goes into an engine oil, or how many naked babes smear it all over their bodies, or how bright and colorful the packaging is, it's what's written on the packaging that counts. Specifications and approvals are everything. There are two established testing bodies. The API (American Petroleum Institute), and the European counterpart, the ACEA (Association des Constructeurs Europeens d'Automobiles - replaced CCMC in 1996). You've probably never heard of the European one, but their (API)stamp of approval will be seen on the side of every reputable can of engine oil in the US and Canada.


The API classifications are different for petrol and diesel engines:

For petrol, listings start with 'S' (meaning Service category, but you can also think of it as Spark-plug ignition), followed by another code to denote standard. 'SN' is the current top grade but 'SH' is still the most popular.
For diesel oils, the first letter is 'C' (meaning Commercial category, but you can also think of it as Compression ignition). 'CJ' is the highest grade at the moment, (technically CJ-4 for heavy-duty) but 'CH' is the most popular and is well adequate for passenger vehicle applications.

Note: Castrol recently upgraded all their oils and for some reason, Castrol diesels now use the 'S' rating, thus completely negating my little aid-memoir above. So the older CC,CD,CE and CF ratings no longer exist, but have been replaced by an 'SH' grade diesel oil.


The ACEA standards are prefixed with an 'A' for petrol engines, 'B' for passenger car diesel, 'C' for diesel with particulate filter, or 'E' for heavy-duty diesel. (The older CCMC specifications were G,D and PD respectively). The ACEA grades may also be followed by the year of issue which will be either '04 or '07 (current). Coupled with this are numerous approvals by car manufacturers which many oil containers sport with pride.

The full ACEA specs are:
A1 Fuel Economy Petrol †
A2 Standard performance level
A3 High performance and / or extended drain
A5 Fuel economy petrol with extended drain capability †
B1 Fuel Economy diesel †
B2 Standard performance level (now obsolete)
B3 High performance and / or extended drain
B4 For direct injection passenger car diesel engines
B5 Fuel economy diesel with extended drain capability †
† Not suitable for all engines - should ONLY be used in engines specifying this fuel efficient grade. Refer to the manufacturer handbook of contact your local dealer if you're not sure.

Mineral oils:
E1 Non-turbo charged light duty diesel
E2 Standard performance level
E3 High performance extended drain
E5 (1999) High performance / long drain plus American/API performances. - This is ACEAs first attempt at a global spec.
E7 Euro 4 engines - exhaust after treatment (EGR / SCR)
Part / full synthetic oils:
E4 Higher performance and longer extended drain
E6 Euro 4 specification - low SAPS for vehicles with PDF (see below)
Low SAPS diesel (Sulphated Ash, Phosphorous, Sulphur)

For diesel engines fitted with a diesel particulate filter (DPF) - a filter unit in the exhaust that takes out the microscopic soot particles. Regular diesel oils used in engines that have a DPF can cause the filter to become blocked with ash. Of course none of this is directly applicable to our turbo Dodge cars except that the higher grade oils are well suited for use in our cars....subject to the formulation however.
C1 Low SAPS (0.5% ash) fuel efficient
C2 Mid SAPS (0.8% ash) fuel efficient, performance
C3 Mid SAPS (0.8% ash)
Many OEM are now using their own specifications to capture these specifications. eg. Mercedes 229.31/51, BMW Longlife 04, VW 507 00 etc.

There is also a trend now towards manufacturfers requiring their own specifications - in this case the OEM specification is the one that needs to be adhered to. If it says BMW Longlife 04, the oil must say this on the pack to be suitable for use.

Typically, these markings will be found in a statement similar to: Meets the requirements of API SH/CD along the label somewhere. Also, you ought to be able to see the API Service Symbol somewhere on the packaging:

Beware the fake API symbol:

Some unscrupulous manufacturers (and there's not many left that do this) will put a symbol on their packaging designed to look like the API symbol without actually being the API symbol. They do this in an effort to pump up the 'quality' of their product by relying on people not really knowing exactly what the proper API symbol should look like. To the left is an example of a fake symbol - it looks similar but as long as you remember what to look for, you won't get taken by this scam.

Amsoil are one of the biggest inadvertent offenders of the fake API symbol. Take a look at one of their labels here on the right. See that little starburst that says "Fuel efficient formula SL-CF"? It's actually not an API-certified SL or CF oil. (To be fair, some Amsoil products are API certified and they do have the correct labeling, but their top-tier products do not). The issue of their lack of API certification on these products caused such a stir at Amsoil that they had to generate a FAQ to answer the most commonly-asked questions.

A Brief History of Time API ratings

Some people have asked about the old standards, and although they're not especially relevant, some rampant plagiarism from an API service bulletin means I can bring you all the API ratings right back from when the earth was cooling. expand/contract the table below to see the ratings.

Grade counts too!

The API/ACEA ratings only refer to an oil's quality. For grade, you need to look at the SAE (Society of Automotive Engineers) ratings. These describe the oil's function and viscosity standard. Viscosity means the substance and clinging properties of the lubricant. When cold, oil can become like treacle so it is important that any lube is kept as thin as possible. Its cold performance is denoted by the letter 'W', meaning 'winter'. At the other end of the scale, a scorching hot oil can be as thin as water and about as useful too. So it needs to be as thick as possible when warm. Thin when cold but thick when warm? That's where MultiGrade oil comes in. For ages, good old 20W/50 was the oil to have. But as engines progressed and tolerances decreased, a lighter, thinner oil was required, especially when cold. Thus 15W/50, 15W/40 and even 15W/30 oils are now commonplace.

The question of phosphorus and zinc.

Phosphorus (a component of ZDDP - Zinc Dialkyl-Dithio-Phosphate) is the key component for valve train protection in an engine and 1600ppm (parts per million) used to be the standard for phosphorus in engine oil. In 1996 the EPA forced that to be dropped to 800ppm and then more recently (2004?) to 400ppm - a quarter of the original spec.

Valvetrains and their components are not especially cheap to replace and this drop in phosphorus content has been a problem for many engines (especially those with flat-tappet type cams like our turbo Dodge cars with slider cams- pre 1987). So why was the level dropped? Money. Next to lead, it's the second most destructive substance to shove through a catalytic converter. The US government mandated a 150,000 mile lifetime on catalytic converters and the quickest way to do that was to drop phosphorous levels and bugger the valve-train problem.


In the US, Mobil 1 originally came out with the 0W40 as a 'European Formula' as it was always above 1000 ppm. This initially got them out of the 1996 800ppm jam and knowledgeable consumers sought it out for obvious reasons. Their 15W50 has also maintained a very high level of phosphorus and all of the extended life Mobil synthetics now have at least 1000ppm. How do they get away with this? They're not classified as energy/fuel conserving oils and thus do not interfere with the precious government CAFE (corporate average fuel economy) ratings. (See my section on the EPA and fuel economy in the Fuel and Engine Bible for more info on this). This also means that they don't get the coveted ratings of other oils but they do protect your valve-train. The same rule of thumb is true for racing oils like Royal Purple - because they're not classified as energy / fuel conserving, it would seem they still contain good quantities of ZDDP...good for protecting ANY cam and even better for the thrust bearing in your turbo! ANY Dodge turbo BTW.

In fact, as a general rule-of-thumb, staying away from XX-30 oils and going to 10W-40 or higher might be the way to go if you have an older engine. 10W-40 and above is generally also not considered to be 'gas saving' and like the Mobil example above, doesn't mess with the CAFE rating.

If you live in England, Castrol market a product with ZDDP in the product description - 'Castrol Classic Oil With ZDDP Anti-Wear Additive' although it's not mainstream enough to be available everywhere. You'll have to find a specialist dealer. Castrol Classics. In the US, Rislone manufacture an oil supplement to boost the ZDDP content of your existing oil. If you use a thinner synthetic oil that doesn't have sufficient ZDDP addative in it, you can purchase a ZDDP booster product to bring it up to the level of protection our engines need. So that means you can go with the 0W20 Mobile 1, get the advantage of a lighter oil, better gas milesage (its like 1/10 mile per gallon) by simply adding the ZDDP additive.

API rating backward compatibility and 2V engines

This section contains information from Bruce Dance, Brian over at bigcoupe.com and LN Engineering and their combined experience with API ratings and 2 valve engines...


If you own a two-valve spark ignition engine or certain diesel engines (which do not have to meet recent emission standards) the only sensible (ie widely available) oil to put in right now is synthetic or semisynthetic to meet API SL/CF and not a higher rating. As I touched upon above, oils with a CG and higher rating typically don't contain enough ZDDP, and the replacement friction modifiers don't work in highly loaded valve trains (generally older engines especially those with 2V design). If you try to compensate by adding a ZDDP additive into a newer oil it still might not work because of interactions with other additives in the oil.

Why the discrepancy in the ratings? The API no longer include a valve train wear test that accurately simulates 2V cam follower loading. They do perform a test that simulates 4V loading and then they allow a lot of wear to occur and still 'pass'. The ACEA tests are a lot tougher but still not tough enough. Whilst the newer CG, CH and higher API oil standards should be 'better in every way', they are really just 'improved in some ways'. Hence the increasing use of manufacturer-specific standards.

There is a lot of info kicking around on the web on this topic because it has caused a LOT of problems with some engines especially Porsche aircooled units.

One of my readers found out when he went to buy oil for his (modern 4V common rail diesel) Nissan that they expressly prohibit the use of CG or higher rated oils. Nissan mandate that owners use CF oils in these engines. It's worth noting that the CF spec was already out of date when these engines were built but Nissan did not use the latest API spec because it wasn't good enough!

The fact that API have dropped the CF tests/standard does not in any way improve the later oils that do not meet this standard.

Marine Diesels and other special considerations.

Inland Marine Diesels (and certain road vehicles under special conditions) can (and do) glaze their bores due the low cylinder wall temperatures causing the oil (and more importantly the additive pack) to undergo a chemical change to a varnish-like substance. The low temperature is caused by operating under light load for long periods.
This is related to engine design, some engines being nearly immune to it and others susceptible. The old Sherpa van diesel engines were notorious for this problem. The "cure" (such as it is) is to use a low API specification oil, such as CC. Certain engine manufacturers/marinisers are now marketing the API CC oil for this purpose under their own name (and at a premium). You'll find some modern engines where its industrial/vehicle manual states API CF and the marinised manual states API CC/CD. {Thanks to Tony Brooks for this information.}

Marine Oils.

I sometimes get asked "why are marine engine oils so expensive and why can't I just use regular motor oil in my marine engine instead?". Well, the National Marine Manufacturers Association Oil Certification Committee (click here for more info) introduced a four-stroke engine oil test and standard called the 4T certification. This specification is meant to assist boaters and manufacturers in identifying four-stroke cycle engine oils that have been specially formulated to withstand the rigors of marine engine operation. The certification was prompted by the growing influence of four-stroke engines in the marine market and their unique lubrication demands. So the simple answer is that regular road-based engine oil products don't contain rust inhibitors and won't pass the 4T certification. Lakes, waterways and the sea are a lot more aggressive an environment for an engine to operate around than on land.
Note : the NMMA have long had a similar specification for 2-stroke oils destined for marine use, called the TC-W3® certification.

Engine oil / Motor oil Shelf Life.

I couldn't decide whether to put this in the FAQ or the main page, so it's in both, because I get asked this question a lot. Typically, the question is along the lines of "GenericAutoSuperStore are having a sale on WickedlySlippy Brand synthetic oil. If I buy it now, how long can I keep if before I use it?"
In general, liquid lubricants (ie. oils, not greases) will remain intact for a number of years. The main factor affecting the life of the oil is the storage condition for the products. Exposure to extreme temperature changes, and moisture will reduce the shelf life of the lubricants. (an increase of 10°C doubles oxidation which halves the shelf life) ie. don't leave it in the sun with the lid off. Best to keep them sealed and unopened.

Technically, engine oils have shelf lives of four to five years. However, as years pass, unused engine oils can become obsolete and fail to meet the technical requirements of current engines. The specs get updated regularly based on new scientific testing procedures and engine requirements. But this is only really a concern if you've bought a brand new car but have engine oil you bought for the previous car. An oil that is a number of years old might not be formulated to meet the requirements set for your newer engine.

If your unopened containers of engine oil are more than three years old, read the labels to make sure they meet the latest industry standards. If they do meet the current standards, you might want to take the extra precaution of obtaining oil analysis before using them. An oil analysis will check for key properties of the oil and ensure that it still meets the original manufacturing specs. Of course the cost of getting an analysis done on old oil is probably going to outweigh going and buying fresh stuff. So it's a double-edged sword.

As a general rule, the simpler the oil formulation, the longer the shelf life. The following is a guideline under protected conditions - indoors at about 20°C:

The following are signs of storage instability in a lubricant:
Settling out of the additives as a gel or sticky liquid
Floc or haze
Precipitates/solid material
Colour change or haziness
Water contamination in a lubricant can be detected by a "milky" appearance of the product.
"High mileage" oils.

More and more oil companies are coming out with "high mileage" oils, some recommended for engines with as few as 75,000 miles on them. So what is a "high mileage" oil you ask? Very generally speaking, these oils have two additives in them that are more suited to older engines. The first is normally a burnoff-inhibitor which helps prevent the oil from burning off if it gets past an engine seal into the combustion chamber. The second is a "seal conditioner", the exact makeup of which I'm not sure of, but it's designed to soak into seals such as head- and rocker-cover gaskets and force them to expand. Thus if one of the seals is a bit leaky, the seal conditioner will attempt to minimize the leak.

I've not had experience of high mileage oils myself, but a few people who've e-mailed me have passed on various tales from it being the miracle cure to it making no difference at all. I think the general rule-of-thumb though should be "if it 'aint broke, don't fix it." Just because your engine has over 75,000 miles on it, doesn't automatically mean you need high mileage oil. Is the exhaust sooty or smokey? Are you noticing oil leaks? Is the engine consuming oil? If your engine is working fine, the exhaust is clean and you're not noticing any problems, my guess is that it doesn't need high-mileage oil.

What about own-brands?

If you can't afford the big-name players, you could look at own-brand oils. These are usually badged oils from one of the larger companies but sold without the name, they are cheaper. Check the standards and grade ratings on the pack first! The example on the left is a local store in Chelmsford in England who sell their own label oil which is bottled for them by a volume retailer. The label tells you all you need to know.

Viscosity and Viscosity Index (VI).

A rough guide to ambient temperatures vs oil viscosity performance.

The proper viscosity is the single most important criteria of a lubricating oil. The basic performance of machinery is based on the viscosity of the lubricant. Viscosity is, if you like, the resistance to the flow-ability of the oil. The thicker an oil, the higher its viscosity. The chart on the right shows a rough guide to ambient temperatures vs oil viscosity performance in both multi-grade (top half) and single grade (lower half) oils.

Multigrade oils work by having a polymer added to a light base oil that prevents the oil from thinning too much as it warms up. At low temperatures, the polymers are coiled up and allow the oil to flow as it's low number (W number) indicates. As the oil heats up, the polymers unwind into long chains which prevent the oil from thinning as much as it normally would. The result is that at 100°C, the oil has thinned only as much as its higher rating. Think of it like this: a 10W30 oil is a 10-weight oil that will not thin more than a 30-weight oil when it gets hot.
The viscosity index of a lubricant is an empirical formula that allows the change in viscosity in the presence of heat to be calculated. This tells the user how much the oil will thin when it is subjected to heat. The higher the viscosity index, the less an oil will thin at a specified temperature. Multi-viscosity motor oils will have a viscosity index well over 100, while single viscosity motor oils and most industrial oils will have a VI of about 100 or less.

Servicing and checking

For God's sake don't skimp on either of these. You can never check your engine oil too often. Use the dipstick - that's what it's there for - and don't run below the 'min' mark. Below that, there isn't enough oil for the pump to be able to supply the top of the engine whilst keeping a reserve in the sump. All oils, no matter what their type, are made of long-chained molecules that get sheared into shorter chains in a running engine. This in turn means that the oil begins to lose its viscosity over time, and it uses up the additives that prevent scuffing between cams and followers, rings and cylinder walls etc etc. When this happens, fresh oil is the key. Don't worry about the engine oil turning black. It will lose its golden-brown color within a few hundred miles of being put in to the engine. That doesn't mean it's not working. Quite the contrary - it means it is working well. It changes color as it traps oxidized oil, clots and the flakes of metal that pop off heavily loaded engine parts. Just don't leave it too long between oil changes.

So how often should I change my oil?

You can never change your engine oil too frequently. The more you do it, the longer the engine will last. The whole debate about exactly when you change your oil is somewhat of a grey area. Manufacturers tell you every 10,000 miles or so. Your mate with a classic car tells you every 3,000 miles. Ole' Bob with the bad breath who drives a truck tells you he's never once changed the oil in his ve-hickle. Fact is, large quantities of water are produced by the normal combustion process and, depending on engine wear, some of it gets into the crank case.

If you have a good crank case breathing system it gets removed from there PDFQ, but even so, in cold weather a lot of condensation will take place. This is bad enough in itself, since water is not noted for its lubrication qualities in an engine, but even worse, that water dissolves any nitrates formed during the combustion process. If my memory of chemistry serves me right, that leaves you with a mixture of Nitric (HNO3) and Nitrous (HNO2) acid circulating round your engine! So not only do you suffer a high rate of wear at start-up and when the engine is cold, you suffer a high rate of subsequent corrosion during normal running or even when stationary.

The point I'm trying to make is that the optimum time for changing oil ought to be related to a number of factors, of which distance traveled is probably one of the least important in most cases. Here is my selection in rough order of importance:
  1. Number of cold starts (more condensation in a cold engine)
  2. Ambient temperature (how long before warm enough to stop serious condensation)
  3. Effectiveness of crank case scavenging (more of that anon)
  4. State of wear of the engine (piston blow-by multiplies the problem)
  5. Accuracy of carburation during warm-up period (extra gook produced)
  6. Distance travelled (well, lets get that one out of the way)

If you were clever (or anal) enough, you could probably come up with a really clever formula incorporating all those factors. However, I would give 1, 2, and 3 equal top weighting. Items 1 to 3 have to be taken together since a given number of "cold" starts in the Dakar in summer is not the same as an equal number conducted in Fargo in January. The effect in either case will be modified by how much gas gets past the pistons. What we are really after is the severity and duration of the initial condensation period. All other things being equal, that will give you how much condensate will be produced and I would suggest that more than anything else determines when the oil should be dumped.

Dammit! Get to the point already!

Hang on a moment - if you really want the answer, there's a couple more factors you need to take account of:

Crank-case scavenging (that's the clever term for sucking the nasty fumes back out of the crank-case) - or lack of it - is a crucial multiplying factor affecting all the other items listed above. As an example, the worst I've heard of was a Ford Fiesta of the mid 70s or so. Its crank-case fume extraction was via a tiny orifice directly into the inlet manifold which obviously could not handle any significant volume of crank-case fumes without upsetting the carburation. The car in question had been used almost exclusively for 5 mile journeys to/from work, shopping etc, and it had always been serviced "by the book". Despite (or because of) this, the engine was totally buggered at 40,000 miles. Alternatively you might get a car that by virtue of excellent crank case fume scavenging could tolerate many more cold starts than one without.

Taking all these into consideration, my philosophy would be to totally ignore the distance and change the oil twice a year - about November and March. Move these dates a bit according to the severity of the winter. An average family car will do around 14,000 miles per year and about 2/3 of that will fall in the March - November period. At the end of that period, the car will be getting close to the manufacturer-recommended oil change interval - but all that distance will have been done at reasonable temperatures, including long distance runs during vacations and good weather. During the November to March period it may accumulate only 2 or 3 thousand miles, all low temperature starts and mostly short runs.

Around 1995, an article in the ANWB journal (ANWB is the Dutch equivalent of the AA - or the AAA in the American case) reached more or less the same conclusion that distance was not very important. In their case they applied this to their road service fleet, which once started in the morning never got cold. In effect, they hardly ever changed the oil. I seem to remember 30,000 miles between oil changes being quoted. I also seem to remember that they had some kind of water or acid indicator attached to the end of the dipstick and went by that rather than distance.

That's a politician's answer - you've dodged the entire issue!

Have I? I don't know how far you drive in a year, where you live, the style of your driving or anything else so I can't tell you what's right for your car. I changed the oil and filter in my 1985 Dodge Charger w/T1 turbo every 3,000 miles. It had done over 150,000 miles when I sold it, wasn't leaking and didn't consume any oil. My other cars got oil changes at 3,000 to 5,000 miles but were newer cars in a warmer environment.

Engines pump about 10,000 liters of air for every liter of fuel consumed, and along with all that air, they suck in plenty of dirt and grit. A good air filter will stop everything bigger than a micron in diameter - everything smaller mostly just floats around harmlessly in the 0.001inch minimum thickness oil films that separate all the moving parts. Despite all of this, there will always be submicron particles that get in and there will be places in the engines oil-ways where they will gather. Every time you empty the oil from your sump, you're also draining this fine grit with it.

Checking the oil in your engine, and topping up.

Where the oil is in a typical engine

Note that this section only applies to wet sump engines - the type found in most consumer vehicles. For more info on sump types, see Wet sumps vs. dry sumps below.

To a lot of people, this little section could be categorized by the rearranging the words "granny eggs teaching suck your to". But you'd be surprised by the number of people that don't know how to do even this basic task. When checking the level of oil in the engine, the car should be on a level surface, and should be relatively cold. I've run into several people lately who insist in keeping the crankcase topped off completely, and they invariably check the dipstick just after shutting down the engine. Checking the oil this way results in an erroneous reading because a quantity of oil (usually about half a litre) is still confined in the oilways and passages (galleries) of the engine, and takes some time to drain back into the crankcase. (On the image, the blue areas are where oil is likely to still be running back down to the sump). On seeing what appears to be an abnormally low level on the dipstick, these people then add more oil to the oil filler at the top of the engine. The oilways and passages all empty, and suddenly the engine becomes over-filled with oil, going way above the 'MAX' mark on the dipstick.

So what's the best way to check the oil level?

If your engine is cold (for example it has been parked overnight) you can check the oil level right away. The oil will have had time to settle back into the sump. Just make sure the car is level before you do. If the engine is warm or hot (after you've been driving) then you should wait for 30 minutes or so to let as much oil as possible drain back into the sump. Checking it first thing the next morning is ideal.

It's worth pointing out that you should double-check your owner's manual too - some cars, like I the '92 Porcshe Carrera, require that the oil is checked while the engine is running and the oil is at temperature.

Wet sumps vs. dry sumps.

Different types of oil sumps

Almost all passenger cars, trucks and SUVs use what's called a wet sump system. If you look at the diagram above you can see the sump (or oil pan) is the lowest part of the engine. In a wet sump system, excess oil drains back into the sump when it has passed through the engine, and the oil pump then sucks it out of the sump and pumps it back to the top of the engine. The advantage of a wet sump is that it's cost effective to build and maintain and it makes oil-checking easy for the average driver. The disadvantage is that cornering and braking can cause the oil to slosh around in the sump. This can cause the oil to not cover the oil pump pickup tube, which could starve the top end of oil, or it could get deep enough in a severe cornering maneuver to bog-down the crank, which is A Bad Thing. To counter these problems, a lot of wet sumps have baffles in them to stop the oil moving around so much, and for your average road-going consumer-level vehicle, this is a fine compromise.

Dry sumps

When it comes to racing vehicles, wet sumps simply have too many disadvantages. Instead, race engines typically use a dry sump. As its name implies, the sump of the engine is dry - it never fills with oil. In a wet-sump system, the sump has to be large enough to accommodate all the oil from the engine when it is turned off. In a dry sump system, that requirement is gone so the sump can be much much smaller. (In the image on the right, the right-most sump is representative of a dry sump). A smaller sump means the engine can be mounted lower down in the vehicle, which in turn lowers the center of gravity - great for racing. So how can this be? Well a dry sump system uses a remote oil reservoir or tank, and a either a second oil pump, or a single multi-stage pump. In a double pump system, one oil pump works just like a wet sump - it distributes oil to the top end of the engine, but it pulls the oil from the reservoir instead of the sump. The second pump scavenges the oil from the sump and returns it to the reservoir. In a single pump system, one pump is either a three- or four-stage pump. It has multiple circuits running off the same pump to pressurize the engine and scavenge oil back from the sump. The pumps typically don't run off the crank-driven belts so no engine power is sapped in driving them. The remote tank or reservoir can be pretty much any size you like and be mounted anywhere in the vehicle (usually low down again for center of gravity reasons). There isn't oil sloshing around in the sump so you don't run the risk of bogging down the crank. For all these reasons, dry sumps are considered to be safer and far more dependable than their wet counterparts. So if it's that much better, why don't you find this system in consumer vehicles? Simple. The increased weight, complexity and cost of having larger or more pumps and a remote reservoir with all the additional high pressure oil lines involved. For a racing team, this isn't an issue, but for Toyota or Ford, adding that sort of cost and complexity to their passenger vehicles is just a no-go.

Can I use car engine oil in my motorbike then?

No you can't. Or at least I wouldn't recommend it....

The real answer to this question lies in the type of motorbike you own. If you own a bike with a wet clutch (ie. where the clutch sits partially submerged in the sump oil) and you dump car oil into it, all sorts of nasty things happen. Oils formulated for car engines have friction modifiers in them. When the engine oil gets into the clutch, the friction modifiers get to work and you'll end up with a clutch that won't bite. In addition, the chemical makeup of some car oils has been known to soften the clutch material on motorbikes to the point where the entire clutch pack fails. Bike oils generally don't have friction modifiers, so they don't have this problem. If you're not sure, check for a JASO MA spec on the bottle. If you see that on the label, then it means the oil has been tested and confirmed to work with a wet clutch. Mobil have cautionary information on exactly this subject on their Motorcycle Oils FAQ page.

The other side of this coin is if you have a dry clutch bike, like some BMWs. In this case, the clutch is configured similar to a car in that it's never in contact with the engine oil, and if that's the case, then regular car engine oil might provide all the protection and lubrication you need for your bike. The issue then becomes a question of the exact formulation of the oil. The additive packages for car engine oil are typically balanced differently than those for motorbikes with fuel economy and emission system protection being the higher priorities. Your typical passenger car doesn't rev to 12,000 rpm either so stuffing normal car engine oil in a motorbike engine that can run to double or even triple the rpm of a car engine could cause all sorts of problems.

The debate about whether any of this is true is burning in many forums across the internet. One site in particular casts some doubt on the issue, claiming the only difference between car and bike oil is the price. I don't subscribe to that theory but in order for you to make your own decision, here's a link: Testing motorcycle oil.

Sulfated ash

There's a second good reason you shouldn't use car oil in your motorbike - sulfated ash. It's common in many American & Canadian modern oils; without burnt oil discoloring it, it normally has a light-gray to pale-tan colouration which may become visible if you shear a bit of the debris. When coloured by oil, it looks like the dreaded sludge. Unfortunately, the API SH-SN ratings are not strict enough on sulfated ash content. It's an issue that's fairly well known in some motorcycling circles, and the Japanese motorcycle industry recognized the issue very early on, creating a new oil specification specific to their needs (one, that among other things, caps the sulfated ash content very low): JASO-MA, recently revised further into to JASO-MA1 & JASO-MA2. For motorcyclists, the sulfated ash content poses a secondary issue: it means higher quantities of sulfuric acid if water gets introduced into the oil (such as from condensation within the galley spaces); since most motorcycle engines share the oil with both the engine and the transmission, the sulfuric acid is particularly problematic as the metals used in the transmission selector forks are made of cheaper steels that don't stand up to the acid nearly as well as most engine components.

Can I use diesel engine oil in my petrol engine?

This is an awkward question to answer. Diesel engines run much higher compression ratios than petrol engines and they run a lot hotter, so the oil is formulated to deal with this. Plus they produce a lot more dirt in terms of combustion by-products. Diesel-rated oils typically have more detergents in them to deal with this (see Using Diesel oil for flushing above). It's not unheard of for diesel oils to clean a petrol engine so well that it loses compression. Diesel-rated oils also have an anti-foaming agent in them which is unique to diesel engines, and not needed in petrol engines.

So is that the be-all and end-all answer? Well not really and that's why this is a difficult question to give a straight answer to. The above statement is more relevant to commercial diesel engines. Nowadays, just about all passenger car / light commercial oils (including OEM ones designed for both petrol and diesel engines) will carry the ACEA A and B specifications. ie. formulated to satisfy the requirements for both types of engine. So just because the oil is labelled "Diesel" doesn't mean it's not suitable for petrol engines - it will more than likely carry an ACEA A3 / OEM petrol spec as well.

However you do need to be a bit careful regarding choosing the right diesel spec - if you have a modern common rail / direct injection diesel, chances are it will require at least an ACEA B4 spec to cope with the higher piston temperatures that can cause piston deposits (and stuck rings). ACEA B4 is fine where B3 is recommended.

And so to engine additives

Your engine is designed to be lubricated by oil, formulated by big petro companies and full of additives that perform anti-wear, heat transfer, lubrication and detergent functions. That doesn't stop dozens of companies formulating extra additives and selling them as pour-in-the-engine and pour-in-the-tank solutions for problems you may or may not have. In the bad old days, these were known as snake oil - back when putting Teflon® in your engine seemed like a good idea. (Here's a famous old snakeoil article.)

In my opinion (and that doesn't mean I'm right) a large number of additives are placebos to put minds at rest. It's not often you'll find properly independent lab analysis of the products that will support their claims. The possible exception to this line of thinking is the ZDDP additive mention herein above.


Not something off Star Trek, although it sounds like it. Nanolubricants use the geometrical properties of miniature particles to provide lubrication. A couple of companies are working on these new generation lubricants; New York-based Applied Nanomaterials (ApNano) is one of them. Their R&D lab in the commercial arm of the Weizmann Institute of Science in Israel is initially developing an onion-type nanostructure, i.e. a multilayered hollow structure of nested spheres called NanoLubTM. According to the theory of the company's founders, such a structure can replace lubricants, because it works like a box moving along a near infinite layer of super-miniaturized ball bearings. They claim that respected institutes worldwide have proved that powder made from these nanostructures is six to ten times more effective than regular lubricants.

In their case, the nanospheres are built from tungsten disulfide (WS2). The layers slide past each other, reducing friction, while the hollow cores provide flexibility. Applied Nanomaterials claims the materials can withstand immense pressures. The material acts as a kind of solid ball bearing between the metal layers, rather like the wheels of a tank tread. In addition, the nanostructures insert themselves within each metal layer, while other nanostructures slide over them, creating a smooth layer at the molecular level.

The idea is that unlike oil, the nanolubricant never wears down; it is permanent and requires no maintenance. Theoretically, a nanolubricant can be used for various friction reducing applications, such as on the outer coating of ships and planes to reduce water and air friction, respectively. If you're that way inclined, think of what it could do to the sex toy industry....

The powder will eventually stand on its own as a lubricant, however Applied Nanomaterials realizes that recognition of the technology requires collaboration with lubricant manufacturers as an additive to existing lubricants. The problem of course is that if this lubricant never needs changing, anyone who decides to mass manufacture and market it is going to lose a chunk of revenue - once you dump it in your engine, you never buy any more. Great for you and me, bad business model for the company who dares to market it.

Applied Nanomaterials competitors are developing similar materials, but based on nested carbon nanotube structures that over time tend to disintegrate under friction from the materials they lubricate.


Don't expect to see NanoLubTM on the shelves in large quantities just yet though. It can take a day to manufacture just 750g of the stuff. At the time of writing, it was being marketed by SONOL Israel Fuel Company

Another player in this brave new world of Things That Are Altogether Too Clever™ is Nanovit, based in the UK.
For the chemists who are reading this, NanoVit builds a nano-scale colloid system at the metal surface and this dynamically changes as the frictional forces are applied to the surface. According to Nanovit, this stuff is based on a structure formed using specific nano-particles of Aluminium Oxide, Silicon Dioxide and Carbon. It does not use carbon nano-tubes and is rated as completely harmless in toxicology testing. It is a permanent coating, existing between many oil changes. The colloid system dynamically "swells" and contracts according to the force and space, causing the resetting of surface geometry to the optimum during the working process of a friction surface, additionally the new surface changes the properties of the thin oil-film layer, interacting with it to improve properties (viscosity index andother key indicators) and protect the molecular structure to prolong oil life. The adherence of the coat to the metal is a bonding process that rebuilds scuffed surfaces and displaces all contaminants (also preventing their re-build up).

For the non-chemists reading this, it's essentially a self-repairing surface right out of science fiction that sticks to the cylinder walls in your engine. Or would that be science friction? Yes, yes, horrible pun. Lets move on.

An alternative to engine additives: pre-pressurization

What the additive manufacturers tell you is true - when you start your engine, there really is very little oil in the right place - most of it is in the sump. There is another alternative. I found a site called AutoEngineLube.com and they seem to be offering an interesting alternative. They have a system which uses a cylinder of pressurized oil and a solenoid valve, all connected to the regular oil system. It works with only one moving part, (the solenoid valve - duh!). When the key is turned on it opens the valve and the oil that was trapped in the tank the previous time it was running goes back into the oil gallery in 1 or 2 seconds and the low oil pressure light will flash off. There's likely to still be a little lag before full-on lubrication gets to the main bearings, but from what I can tell, this system will massively reduce that lag compared to starting from cold - it pressurizes the system before the starter engages. Of course an engine that has set up for a few months and is completely dry will take a few more seconds. When the engine is turned off the solenoid valve shuts off in 30 milliseconds so you end up with pressure on the tank equal to the pressure the last time it was running. The tank will hold more than enough oil to accomplish this. Its completely over engineered as the tank is rated for over a thousand pounds and the hose is good for 300lb. Because the valve is designed for an industrial application with an expected duty life of several million cycles, AutoEngineLube give it a lifetime warranty. It only uses previously filtered oil from the gallery so no damage can be done by it in any way.

Their system comes as a kit and requires some menial installation - most savvy home mechanics should be able to do it. I'm not sure how it would affect the warranty on a car engine. In theory, if it works, it ought to make no difference but you know what manufacturers are like - if you even sneeze on your engine, it's likely to void the warranty.

Pop over and check them out if you're interested. If you end up buying one of these, I'd like to know what sort of results you get so I can add an objective review to my site. AutoEngineLube.com Another site sells a similar product - PreLuber.com....which is now a defunct site but a Google search will yield you the current distributer of that or a similar product. It's not cheap BTW, like $500+.

It's worth pointing out that pre-lubers have been around for quite a while; the original systems featured an electric pump that circulated the oil from the sump before the starter turned. The pump would bring the oil up to full operating pressure before you attempted to start the engine. A reader of this site e-mailed me about this. He had one on an old MG-TD, because the car got very infrequent use; it worked rather well and he never had any major engine problems with it installed. Enginelube.com still do the "old style" pre-lubers but their website has vanished so I don't have a good link for them now.
Oil filters and filtration.

Thanks to one reader who noted that in all of this page, until mid-2001 I had not given much, if any space, to the topic of filters and filtration. So here we go.

This is an exploded view of a typical spin-on oil filter used in automotive applications. I've sliced the filter element (the brownish-yellow part) so you can see the internal structure of the filter). Typically the engine oil enters through the ring of 5 or 6 holes in the base and into the main cannister. From there it is forced inwards through the filter element, through the drain holes in the central core and out through the central, threaded hole in the base.

It's all very well changing your oil often, but it's not just the oil that helps prevent engine wear. The oil filter does its part too. Dirt is the prime cause of engine wear. Not big dirt, like you'd see in a yard, but minute particles of dirt. It's dirt nevertheless, and it's abrasive. These contaminants vary from road dust (which are razor-like flakes from an engine's perspective) that doesn't get filtered out by the air filter, up to actual metal particles - the byproducts of the casting scarf from the original engine manufacture, and basic engine wear. All this nastiness is carried around by the oil into the minute parts of your engine, being rammed into the precision clearances between bearings and other moving parts. Once in, they don't come out easy, but tend to stay there, wearing grooves, grinding and generally messing up your engine. Other debris that causes problems are a by-product of the mere way an engine works - sooty particles from the combustion process can be forced past the piston rings and transported around in the oil too. This is definitely A Bad Thing - the soot acts like a sponge and soaks up other oil additives reducing the oil's anti-wear properties, and messing up it's viscosity. All this dirt is why oil goes black when it's used. That lovely syrup-like yellow that it is when you put it in is pure oil. The black stuff that comes out at an oil change is the same oil full of contaminants and by-products from wear and tear.

Spin-on oil filter

That's where the oil filter comes in. It's job is to catch all this crap floating around in the oil, and to stop it from recirculating. Most oil filters that you or I will ever see are the spin-on type. They're shaped like an aluminium can and spin on to a threaded oil feeder poking out of the side of the engine somewhere. They're called 'full-flow' oil filters because they sit in the normal flow of the oil through the engine. Sort of like an electrical component in series with all the other electrical component. Because it sits in-line, it has to be designed not to restrict the flow of oil around the circuit, and thus can only really be effective at stopping the larger particles. Large, in this case, is around the 20micron size. So here's the catch. The smallest contaminants are in the 10-20micron size range. Not only is that "extremely small", but it means that they pass right through the oil filter and back out into circulation. This is why regular oil changes are a necessity, because these tiny little things can be the most damaging.

There is another alternative, but it's only really used in heavy applications or for racing. That alternative is to fit a secondary bypass oil filter. This is sort of like a filter in parallel with the primary one. It doesn't restrict the flow of oil in the main circuit, but the oil that passes through it is filtered down to the 5 micron range, thus removing even the smallest contaminants. The newest filters claim to work down to 1 micron, though I can't confirm nor deny those claims. The upside is that by cleaning the oil so completely, bypass oil filters increase not only engine life, but also the life of the oil itself. This means longer service intervals.

Magnetized oil traps

Recently, magnetic filter additions have started to surface. I was sent one in 2001 to try out and it really did seem to work. The product in question was called the Bear Trap BT500. Their website can be found here (now owned by One Eye Industries). It's basically a sleeve made of foam rubber and plastic with some magnets in it. It bends to clamp around the outside of your regular spin-on oil filter. The idea is that the magnets will attract any metal debris in your oil and stick them to the inside of the oil filter wall, thus preventing them from going back into the oil circulation. Being of a curious nature (or stupid, depending on how you look at it) I decided to dismantle my oil filter after using the Bear Trap for 5000 miles. I learned a couple of things.
  1. You shouldn't try to do this yourself.
  2. It's bloody messy.
  3. But most importantly, after a brief period in accident and emergency to stitch up the gash in my hand, I discovered that sure enough, there were tiny arrangements of metal filings clustered around the inside of the oil filter wall where the magnets from the beartrap had been. You'll excuse the lack of photos to prove the point, but I had other things to worry about. If you visit their website or that of FilterMag (below) you'll see similar cutaway photos.

So can I recommend their product? Yes.

Another alternative to the Bear Trap is the FilterMag - essentially the same style of product but from a different manufacturer.

An alternative to custom magnetized oil traps.[/COLOR]

Thanks to John Nightingale who read my pages and then felt he should contribute something. For those of you who do more than just change your filter - ie. take off the oil pan completely, John writes:
" Next time you are in the mall or high street, drop into the Radio Shack or a hardware store and purchase a package of modern, powerful ceramic magnets. These are available in various shapes and they are cheap. Radio Shack sells a package of two wafer shaped magnets, for instance. Stroll out to your car at the end of your shopping trip, bend down and stick these magnets onto convenient flat surfaces the bottom of your oil pan either side of the drain hole or as convenient. Now the magnets will magnetize the steel of the oil pan in their area. On the inside, particles coming through the field established by a magnet will be sequestered by being stuck to the bottom of the oil pan. Next time you take off the oil pan, clean it out in the usual way, pull off the magnets from the outside, clean them up and then stick them onto the inside of the oil pan at the bottom but clear of the drain hole. This will give an even better result since now the oil is exposed to the naked magnets themselves. The bottom of the oil pan in the area of each of the magnets is also magnetized, of course, and contributing to the effect. Resist the temptation to stand the magnets on edge to expose more of their surface to the oil. Placing the magnets flat on the oil pan uses the oil pan's steel as a keeper for the magnets and will ensure that they stay powerful. Placing the magnets flat will increase the area of the oil pan that is part of the magnetic circuit so you will loose no particle pick up area by having the magnets lying flat. "

Magnetised oil traps - doing it yourself.

There's nothing really special about magnetised oil traps other than the type of magnet they use. Bear Trap and FilterMag basically offer a consumer-oriented product. But if you're a tinkerer, there's nothing to stop you doing it yourself. The magnets normally used are Neodymium, nearly the most powerful nonelectric magnet type. They are the kind of magnet used in computer hard drives, often coming in pairs held just a few millimeters apart with the back end of the hard drive head assembly (the part being made of coiled wire) in between. If you can find a couple of old hard drives - try the local computer junk store - you ought to be able to disassemble them and take the magnets out to stick to your own oil filter. John Nicholas Sarris, a reader of my site, suggested this and provided the following photos as an example.

An open hard drive. The magnets (one visible) are in the upper left corner and are crescent shaped.

The top magnet plate has been removed. As you can see on the lower magnet it is attached to a metal plate. I presume this it to keep the magnetic field from the magnets between the two magnets and not extend outside the hard drive case.

The hard drive's head assembly has been removed. The lower magnet attached to its plate is clearly visible.

A pair of hard drive magnets side-by-side. They are still attached to their metal plates because the adhesive used to attach them is immensely strong. I once removed a hard drive magnet from its plate, but broke it in half in the process.

The same magnets holding themselves to my hand. I could have them stick to each other through my palm, but it was hard to take a good picture. This actually hurt my fingers a bit. As you can see they are strong despite being only 2mm thick. The plate they are attached to itself is 3mm thick.

The importance of neodymium magnets

I thought it worth pointing out here what a potential disaster awaits the home tinkerer if you just grab any old magnet and stick it on the outside of your oil filter. Your common or garden ferrous magnet, like those horrible souvenir magnets stuck to your fridge (you know you've got some) are usually made from iron, and thus have a limited life span which in some cases can be as short as 6 or 12 months. During this time they progressively lose their power. Not enough for that hideous magnetic photo frame to drop off the fridge, but enough to be a problem if it was stuck to your oil filter. Why's that then? Well, come the end of the filters life, just as the magnet is weakening and the collection of metal particles is at it's highest, one good jolt and it could dislodge, and a large collection of metal shavings and filings could detach from the inside of the filter and find its way back into your engine all in one go. That would be bad. So as much as you might like the magnetic photo of granny and the giraffe from Whipsnade zoo to be stuck in a filthy oily place on your car, don't do it.

Larger filters on standard cars?

There's a school of thought which says that enlarging the oil filter on your car is A Good Thing. Why is this?
The small oil filters fitted to engines these days run with quite a high back pressure, and the bypass valve trips at about 3500rpm. That means that your oil is not being filtered when the engine is spinning faster than 3500rpm. As the oil filter does its job and starts to clog up, that rpm value can be lower.

If you increase the size of the filter, this will raise the rpm at which the bypass valve will switch. With a bigger filter and lower back pressure, for the same rpm (prior to bypass valve operation) less engine power will be lost in the filter. Bigger filter means better filtering and more power at low to mid revs. Clever eh? But there's some things you need to be aware of if you're going to try this approach, all of which are relevant, and none of which I can confirm or deny

Bigger filter = more "dead" space = more oil. Remember you'd need to add more oil to the engine to keep the oil level at the correct mark on the dipstick. This isn't necessarily a bad thing - more oil doing the same job theoretically means less stress on the oil.

Oil may take a little longer to circulate around the engine after start-up, as the pump may have to fill up the larger capacity oil filter. Note the oil filter that back-flow preventer (anti-drain-back valve) doesn't help here because it does eventually allow the oil to drain out of the filter with the engine switched off. Anti-drain-back refers to the function of keeping the unfiltered oil from draining back into the engine - it eventually passes through the filter and drains out the normal way.

Availability of filters and fouling. If you put a larger filter on it might foul something else in the engine bay. That is if you can find a larger filter to start with. The rule of thumb is to go to a motor factors shop, and find the oil filter that was designed for your engine .Then look through the myriad of larger oil filter boxes for a bigger filter that has the same screw thread and sealing ring diameter. Nowadays most spin-on filters have a 20mm screw thread so that's not going to be the hard part. Finding the same sealing ring diameter is the thing to be careful of. And don't ask the people at the parts counter. Because of liability issues, they're unlikely to sell you anything other than exact filter for your make and model of vehicle.

This is all great. Now how do I actually change my oil?
Using oil extractors

An example vacuum oil extractor.

There's another way of getting the oil out of your car's engine during an oil change - oil extractors. The typical extractor uses a vacuum mechanism either generated by you pumping a handle to build up a vacuum in the reservoir, or by a powered vacuum pump. The example on the right is a manual style. Basically you pump the handle to build up a vacuum, then poke the extractor hose into the oil and let her rip.

Extractors are a convenience item designed to eliminate the need to get your vehicle up on a ramp, or for you to crawl under it and deal with the drain plug. The only problem with an extractor is that you can never be 100% guaranteed that you get all the oil out. For it to work best, the suction hose needs to be in the lowest point of the sump pan, where the drain bolt is. The problem is that first of all, the sump isn't transparent, so you can't tell where the suction hose really is. (Remember you'll be feeding it in through dipstick tube). Second, a lot of sumps have anti-slosh baffles in them both horizontally and vertically. If you don't get the extractor pipe through one of the baffle holes, you'll be leaving the entire sump's-worth of oil in there. Third, and finally, any congealed oil, clogs or clumps of sludge will likely get stuck in the extractor hose causing a blockage. That would mean taking the hose out, cleaning out the blockage, then feeding it back in again which subjects you to the initial two problems all over again.

Oil extractors are more commonly used for getting oil out of smaller engines like lawnmowers. I've never used one in a car engine but because of the problems mentioned above, I can't imagine it would be especially efficient. Having said that, the Smart car has no sump drain so the only way to get oil out of those things in a service is to use an extractor.

Finally, and just as importantly:

Disposing of used engine oil.

Think about it for a minute. What did you do with that last oil change? Pour it away down a drain? Seal it and bin it? The annual average for oil which is just washed away is 720Million gallons! About 120Million of that is from tanker spills which leaves another 600Million from domestic and business disposal. This all ends up polluting the groundwater.

So what can you do? Well, you can dispose of your used oil properly. Firstly, it's worth noting that engine oils which have been used are mildly carcinogenic. This means cancer, specifically skin cancer. To be safe, wash any off quickly with a de-greaser like GUNK. For heavens sake, don't use petrol (gasoline) - most fuels contain long chain hydrocarbons, which when exposed to skin pass right through to the blood stream. (This can mean liver damage, and possibly failure) Better still, wear protective gloves.[/COLOR]

Once the oil is drained into a suitable container, try your local garage. All garage workshops must have disposal barrels and many will allow you to dump your oil into their barrels. In the UK, many DIY superstores now have oil disposal banks where you can empty your used oil, and it's collected every couple of days by a tanker. So next time, just think about first. If only for the fact that in most civilized countries, it's actually an arrest-able offence to dispose of oil in the public sewerage system.