When answering the question what are engine oil additives, we need to first understand what engine oil does.
Engine oil has two main purposes:
1. It lubricates all moving parts of a car’s engine to minimise friction between parts
2. It protects metallic surfaces from corrosion (rust)
To enable oil to effectively fulfil these two purposes it must be able to travel freely through a car’s engine and coat all the engines components. If engine oil is too thick it will struggle to travel freely enough and could even clog up the engine whilst if it is too thin it travels too quickly through the engine and doesn’t coat all the engine parts.
The problem in car engines is the change of temperature, from a relatively cold environment when you first start your car (especially on cold mornings) to a high-temperature environment when you have been driving for some time. This change in temperature can alter the thickness of your engine oil. When engine oil is cold it will be thicker and as it gets warmer it becomes thinner, this means oil may get too thin to be effective any longer.
Furthermore the heating of engine oil can cause engine oil to oxidise (combine with oxygen and lose hydrogen) which causes the formation of sludge, varnish, resin and corrosive acids which can negatively affect the engine and can cause corrosion (rusting) of engine components.
In order to combat both of these effects it is necessary to add additives to engine oil to help improve its ability to perform its two purposes.
What types of engine oil additives are there?
There are a number of common engine oil additives and they all have different functions;
The problem with VIIs is that they are prone to shearing (i.e. they break up) which prevents them working efficiently and is one of the reasons engine oil should be regularly changed.
Graphite or molybdenum are often utilised for this purpose.
What’s more in engines which have a variable camshaft timing the motor oil must also act as hydraulic fluid, which aerated oil is unable to do.
However some older vehicles that have a flat-tappet camshaft or have an altered engine with higher spring pressures still need an engine oil that includes ZDDP.
Different engines need different oils
Most engine oils on the market today come with pre-added engine oil additives. However different engine oils on the market have different levels of additives, so it is important to check in your owner’s manual which engine oil is recommended for your vehicle.
Engine oil has a shelf life and over its life, the additives within engine oil degrade. Once engine oil additives begin to degrade the engine oil starts to become less and less effective.
Regular oil changes are therefore really important to ensure your oil is always working at its best. If you book an interim service at Stoneacre we provide an oil check as standard to help look after your engine.