What causes engine oil consumption?

Here is a popular question when it comes to engine oil among mechanics, lubricants sales reps, consumers, and everyone in between: why does engine oil get used up? Let’s take a look at the 5 most important reasons.

Oil consumption: 5 common causes

1. Oil consumption is sometimes caused by mechanical problems. Seals and gasket, the bearings, cylinders, ring grooves, connecting rods can be worn or damaged.
2. Cylinders that were not honed properly when the engine was built (or rebuilt), incorrect installation of the piston ring, or other improperly installed parts.
3. An engine loses ability to retain the oil as it ages. Failing to change engine oil in time is another cause for oil consumption.
4. Higher than appropriate viscosity. ‘Thick’ oil tends to remain on the cylinder wall. As a result, it is lost through misting and evaporation.
5. Lower than appropriate viscosity. ‘Thin’ oils cause problems like fuel dilution and wear of the piston ring liner.

Are these the only reasons?

Absolutely not. In addition to the factors above, oil consumption varies from engine to engine. Differences in engine design cause oil to behave differently, even in newer engines.

So how much oil gets consumed?

In passenger cars, typically 0.1-0.3 % of the fuel consumption is consumed in oil. So for every 100 L of fuel you burn, you are losing 0.1-0.3 L of engine oil. 

Even within the same series of engines consumption may vary: about a fifth of the engines have a significantly higher or lower oil consumption than average.

Can I minimise oil consumption by choosing a particular product?

It’s extremely hard to attribute differences in oil consumption to different (but similar) engine oils. In case of a lubricant test, you would need to replicate the exact condition of the engine and other car parts.

Looking for the best ways to decrease consumption and reduce top-up time? Here are three tips:

• Check a car for mechanical problems
• Change the oil in time
• Use the correct viscosity grade as defined by the manufacturer, or use the recommendation feature.

Summary:

Common causes of oil consumption are: mechanical problems, incorrectly installed parts, aged oil and wrong viscosity.

• To make things more complex, oil consumption varies from engine to engine.
• Checking a car for mechanical problems, changing the oil in time and using the correct viscosity grade are tactics to minimise consumption.