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Exploring the functions of engine oil

The main purpose of engine oil is to reduce wear and friction, but this dedicated lubricant performs many other important jobs to keep vehicles running safely and smoothly. In the following sections, we’ll look at what engine oil does, and some of the key functions a reliable product will deliver to vehicle owners.

Minimising friction and reducing wear

As mentioned, this is the primary role of engine oil. The lubricant forms an oil film over metal surfaces of engine parts and reduces friction when they meet. Reduced friction stops abrasion and parts like engine bearings overheating.


Oils also keep engine components clean. To keep an engine’s internal workings well-maintained and free from debris and unwanted deposits like sludge and varnish, engine oil suspends the contaminants it comes across within and stops contaminants from becoming attached to engine parts.

Base oils have a degree of solvency. Solvency is a fluid’s capacity to efficiently dissolve a solid, gas or liquid. This process assists engines to stay clean internally. However, dispersants and detergents in engine oil also play an important role in maintenance.

Dispersants are technically additives that ensure contaminants stay suspended in the oil. A dispersant will act as a solvent to help the oil stay cleaner and stop sludge forming.

Detergents are also additives that inhibit contaminants from adhering parts, particularly hot components, like piston rings.


Reducing friction decreases heat in moving components. This lowers the operating temperature of equipment during use.

Lubricants like engine oil also absorb heat from various surfaces in contact and transfer it safely to a place where it can be safely dispersed – for example, a vehicle’s oil sump.

This transferability is often an attribute of a product’s base oil viscosity. As a rule, a lighter oil will more readily transfer heat.


Engine oil acts as a seal in certain areas like the combustion chamber. The oil seals piston rings from the cylinder wall, preventing hot exhaust gas released from contaminating the lubricant to maximise engine compression.

Dampening shock

A robust lubricant film has the ability to resist a rupture and can absorb and then disperse energy spikes effectively. As a mechanical shock is dampened, damage and wear are minimised, extending the life of engine parts.

Preventing corrosion

Engine oils must also prevent or reduce the corrosion of internal components. To achieve this, the lubricant must either chemically neutralise corrosive material or form a barrier between the corrosive element and an engine’s components. If rust or corrosion form, contaminants can potentially peel off and enter the oil, and from here, they can circulate the engine, damaging components and bearings.

Transferring energy

Finally, due to the fact that lubricants are not compressible, they are able to act as a medium for energy transfer, as seen in hydraulic equipment and the valve lifters of automotive engines.

Systems designed to provide variable-valve-timing can be found in newer engine models. These also use engine oil as a dedicated hydraulic fluid that can actuate components. However, the oil must stay clean and keep its viscosity to successfully fulfil this function.

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