Engine oil: Understanding oil additives

December 26, 2017 8:00 am

In the last few articles we have looked at the uses of additives in oils. Specifically, we pointed out that in mineral-based oil a viscosity additive is a must to be ready for modern cars since it is naturally monograde.

The use of other oil additives is usually considered unnecessary or even bad for the engine. However it’s not an exaggeration to say that all commercial oils contain other additives. Some brands explicitly say it and others don’t, but every oil needs them.

Standard additives in oil

On average, the final lubricant contains 80% base oil. The other 20% are additives mixed with the base oil in order to add some necessary qualities. Apart from viscosity additives, other common ones could be:

  • Cleaning additives: Without these additives oil could easily generate rust, oxide or sludge and could even break down. These additives are mainly detergents, antioxidants or metal deactivators.
  • Contamintant control additives: Soot, carbon or acids can appear in your oil system. That’s why there are necessary dispersants or anti-foam additives which aim to prevent malfunctions.
  • Lubricity additives: Nanoparticles, friction modifiers and extreme pressure agents help significantly reduce friction in the engine.

Most of these standard additives formulate a well-rounded oil which should be enough for regular use. However you may need oil additives for specific cases such as to regenerate seals or to completely clean the oil system.

Also, although some manufacturers claim that their oil can’t get any better, there is another step.

Graphite - A solid additive

Solid additives in oil

What do we mean when we say solid? We are referring to those particles that stay suspended in the oil while keeping a solid state. They do not alter the chemical balance of the oil but they add quantifiable improvements.

Their main use is simple to explain. Inside the engine are metal to metal friction points which, in the absence of oil, would completely wear down. Thanks to the oil these critical points are less prone to wear, however there are still small irregularities in the metal surface that can generate power losses.

To avoid this issue, solid additives in oil create a film over the surface which drastically decreases friction in a way standard oils can’t. Molybdenum, PTFE (Teflon™), graphite and, more recently, ceramic are great examples of this kind of additive.

As a side note it’s worth mentioning that even those small metal particles from friction are solid additives. Large particles, however, are impurities that are then captured by the oil filter. If you want to know more, the science which studies this behaviour is tribology.

Stay tuned!

If we have your attention, stay tuned! We will go deeper into this topic in future weeks.