10 Things You (Probably) Didn’t Know About Oils

1. Viscosity is only one - and not even the most important - aspect of the oil

Viscosity is usually the second most visually prominent information on an oil can, right after the brand name or product name. Many people assume that two oils with different viscosities differ ONLY in their viscosities. However, in reality the differences in the oils’ specifications and OEM approvals not to mention the differences in their base oils are a lot more important. Because cars of our time usually need their factory approved oils in order to maximize their life expectancy.

2. Synthetic oils surpass their mineral counterparts in lubrication, engine cleanliness and heat dissipation

Synthetic oils are formulated from synthetic base stocks so their properties are exactly as they were designed in the lab. Mineral oils are formulated from mineral base stocks (refined crude oil), which are then enhanced with additives to improve their preexisting, subpar properties. Even though additives can significantly improve their properties, mineral oils can never achieve the same quality as synthetic oils.

3. The oil drain interval specified in months is equally important as the one specified in miles or kilometers

Many people think that if they barely use their cars then the oils drain interval can be extended in time, since only the driven mileage counts. In reality, a motor oil starts deteriorating as soon as it is first used. The contaminants that are formed in the oil sustain this deterioration process even when the car is not in use. Furthermore, statistics show that cars that are driven relatively little in a year, are usually used for shorter distances, which account for bigger specific load and stress to the engine and the oil. The reason behind this is that shorter distances mean that more miles are driven with cold engine and since these shorter distances usually mean city driving, the stop-and-go driving situations in the traffic jams and from stop light to stop light also result in more stress per mile for the engine and for the oil. This is why car manufacturers specify the oil drain interval in months as well as miles and this is why the former is as important as the latter.

4. A black motor oil does not mean that it is bad quality or that it needs to be changed

One of the duties of the motor oil is to keep insoluble contaminants in suspension and not to let them form deposits in the engine. This means that motor oils many times get black soon after their first use. Especially in diesel engines, which produce a lot of soot. This does not mean that the oil is bad. Quite the contrary: it means that it does its job. Even though it turned black, it will still do its job until the end of the drain interval.

5. Oil consumption is rarely caused by the oil itself. Most likely it's your engine.

A lot of people think that if a car consumes oil then something is wrong with oil, or it’s not the right oil for that car and it should be filled with a different, usually higher viscosity oil that it likely will not consume. The truth is, however, that oil consumption is most often caused by an engine that is in a bad shape: the engine and/or the seals are worn. If it is a new car then probably the piston rings are designed in a way to produce less friction (to decrease fuel consumption, because less friction means less energy lost), which also results in larger gaps between the pistons and the cylinders also leading to higher oil consumption. Whatever the cause of the oil consumption is, using a higher viscosity oil means treating the symptoms, not the underlying cause. Also, it might even mean worse protection for the engine if by using a higher viscosity oil we step outside the viscosity guidelines of the vehicle manufacturer. Oil consumption rarely damages your engine, using an oil that’s viscosity is too high, in order to reduce oil consumption, may very well do.

6. The edition (year) of the ACEA specification is important

ACEA specifications replaced CCMC specifications in 1996 and there have been many editions since. 1996, 1998, 2004, 2008, 2010, 2012 and 2016 all brought new iterations of the ACEA specifications. One of the most important among these was the 2004 edition where the A (gasoline) and B (light duty diesel) classes were merged and the C class (for catalyst compatible oils) was released. The ever-newer iterations of the ACEA specifications demand more and more from motor oils in every way. Considering either wear protection, engine cleanliness, fuel economy or other properties there are huge differences between – for example - two A3/B3 quality oils if one is ACEA A3/B3-04 and the other is A3/B3-16. Many oil manufacturers have this edition related information included with the specification number (as in our example), so an ACEA C3-12 means that the oil meets the ACEA C3 specifications that were in effect in 2012. ACEA does limit how long an out of date specification can be used. After December 1, 2017, no more new claims are accepted for ACEA 2012 specifications and oils with this now out-of-date specification cannot even be marketed after December 1, 2018.

7. Cars with diesel particulate filters usually require special oils

Ash is the enemy of diesel particulate filters. All motor oils contain ash, some to a higher, some to a lower degree. Cars equipped with diesel particulate filters need oils with reduced ash content so the clogging of the particulate filter can be avoided. If you ask how would the ash from the oil end up in the DPF, the answer is because all engines consume motor oil. Even those that seem not to. Many can manufacturers have their own specifications for reduced ash content oils (e.g. MB 229.31 and MB 229.51 for Mercedes Benz). Other manufacturers recommend using an oil meeting one of the ACEA C specifications. Using the incorrect oil may result in the DPF’s early demise.

8. It’s risky to add extra additives to a motor oil

Motor oils are formulated as mixtures of base stocks and additives. The base properties of the oil are determined by the base stocks and those properties are further enhanced by additives. These additives are in a careful balance to optimize the oil for the best combination of lubrication, heat dissipation, fuel-economy, anti-corrosion and other properties. When we add an extra additive to the mix we may very well disrupt the balance of these factory additives and in our effort to improve one property of the oil (usually the lubrication) we decrease the oil’s ability to perform its other duties (usually the heat dissipation). We must accept that motor oils are complex products and the engineers designing these products know what they are doing. We should not try to modify the mixture they created and carefully balanced. By doing so we not only jeopardize the engine, but we may also void the warranty.

9. 4-stroke motorcycles usually need special oils

Many people think that a 4-stroke motorcycle requires a regular motor oil like a car. Both have 4-stroke engines after all. In reality, however, in most modern motorcycles the motor oil is also responsible for lubricating the transmission and the wet clutch. Such motorcycles need special motor oils that can perform these duties as well. Modern passenger car motor oils contain way too much friction modifier additive to be able to handle these tasks. The solution is the appropriate 4T oil that meets the motorcycle manufacturer’s specifications. In most cases this means a JASO MA type oil.

10. Motor oils usually aren’t too thin when hot but they are too thick when cold

A lot of people like to choose high viscosity grade motor oils assuming they provide better protection, especially when hot. They worry that a hot, low viscosity grade motor oil would not create a strong enough oil layer and engine wear would be more significant. The truth is, however, that most of the wear occurs at cold starts. An oil with a lower viscosity grade can provide better protection at cold start because it takes less time for it to reach its optimal viscosity (in layman’s terms thickness) so the engine runs less time not fully protected. To also address the problem of the thinner oil film at high temperatures: the oil film’s strength is not determined solely by its thickness. Modern synthetic oils provide very thin but very strong oil films. If that was not the case there could not be 0W20 and 5W20 oils at all, since they would be incapable to protect the engine with their film thickness alone.