What Engine Oil Does My Car Need?

All motorcars, whether boasting electric, or internal combustion, propulsion require lubrication to stop parts from rubbing together, overheating, wearing and failing. Engine oil is the most common lubricant used but they differ considerably, depending on the component.

While this blog provides a basic overview, modern cars have exacting lubrication requirements and so prioritise your car maker's specification, when selecting lubricants. Dosing any part of a motor car with an incompatible lubricant can cause mechanical failure and is likely to void the warranty.

What is engine oil?

Motorcar oil comprises base oils, based usually on crude oil. These are refined and combined by specialist chemical companies with semi-synthetic additive packs to give the necessary performance characteristics to your required oil type.

What does engine oil do?

Engine oil lubricates and transfers heat energy away from highly stressed components. Most modern cars require synthetic oils, which tend to be those with high-quality base oils. Additive pack compositions vary considerably. Engine oil for classic cars tend to have fewer detergents, whereas those for diesel possess complex cleaning chemicals within their formulations.

The latest engines also need additives for engine oil to protect their timing chains/wet belts, prevent low-speed-pre-ignition and curtail intake coking. Extra additives also protect rubber seals, neutralise harmful acids and reduce the natural tendency for the oil to turn into sludge, as it oxidises. This explains why you need to do a engine oil check as engine oil needs periodic changing.

What is gear oil?

Gear oils are employed by manual transmissions and axles/differentials. Due to the high forces experienced between the gears, an extreme pressure lubricant tends to be required, hence why many of these products are labelled 'EP'.

These additives account for EP gear oil's pungent smell; they also can be corrosive. This is why you should not deviate from the oil recommended by the carmaker. For instance, using a GL-5 lubricant in a component requiring GL-4 could corrode any soft metals used inside.

While draining and refilling transmissions tends not to be a service requirement, we are seeing an increasing number of Battery Electric Vehicles aiming to find the right oil that requires periodic replacing, due possibly to the high torque levels their transmissions must tolerate from the electric motor.

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