What does a motorcycle oil actually do?

Ok, so you know you need to use a good quality motorbike oil in your engine, but what exactly does the oil do?

In it’s most basic terms, the oil coats the engine parts with a film, which means the metal parts don’t rub against each other when they move, spin or slide against each other (as metal rubbing on metal is bad!!).
Modern oils are also designed to provide other forms of protection in the engine.

Main objectives of a motorcycle oil..

There are 5 main functions of a motorbike oil.

1) Oil minimises engine wear

Fairly self explanatory, oil is designed to cover moving parts in a film, as the metal parts move and rub against each other, it’s actually the protective oil film that absorbs most of the wear (or all of the wear in the case of a good, fully synthetic oil).

2) Oil keeps the engine clean

Obviously, engines are dirty! The process of the engine running creates quite a bit of dirt ( metal particles, carbon and other nasty bits). Oils are designed to clean and prevent the build up of dirt in the engine.

3) Oil helps to disperse combustion by-products

The process of combustion (the ‘bang’ as fuel is burned in the cylinder) is very dirty and the dirt created by this reaction needs to be dispersed or else it will build up in the cylinder and render the engine unable to run after a while.

Exhausts help to get rid of some products (gases) but other, solid products (like carbon) need to be removed by the oil.

4) Oil helps to transfer heat from some parts of the engine

Engines get very hot while they are running, oils help to transfer heat away from hotter areas of the engine (like the cylinder).

5) Oils help prevent engine rust

If you’ve ever looked at your brake disc after the bikes been left for a few days, you can sometimes see a build up of rust on it. This could happen inside an engine, which would be very bad if it wasn’t for anti rust additives in oil and the film of oil on the engines internal parts.

Secondary objectives of a motorcycle oil

There are 2 secondary functions of a motorbike oil.

1) An oil needs to remain effective whilst in the engine

You need to know that if you’ve put a 10w40, semi synthetic oil in your engine when you serviced it, that it is still a 10w40, semi synthetic when you drain it out 5,000 miles later.

This is important as if the oil breaks down after 1,000 miles, it won’t be protecting your engine properly!

2) An oil must be able to perform over a wide temperature range

We don’t all ride the same bike at the same speed and all live in a place where the temperature stays the same so oils must be able to perform whether it’s winter or summer and be able to cope when the engine is cold or if it’s hot.

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