Engine Oil Consumption

Purpose of Engine Oil

Engine oil lubricates moving parts and reduces friction-generated heat. Oil plays a critical role in maintaining engine performance.

Oil consumption

A small amount of oil consumption is normal for a serviceable engine. Increased engine oil consumption may be caused by the following.
Oil lubricates the pistons, piston rings and cylinders. An oil film between the piston and cylinder is carried by the piston during its downward movement on the intake or power stroke.
During engine braking, a vacuum is created which draws the oil film and oil on the cylinder walls into the cylinder, and the oil then burns in the hot combustion gases.
Oil is also used to lubricate the intake valve stems.
Some oil is drawn into the combustion chamber and burns together with the fuel.
High-temperature exhaust gases also burn off oil that lubricates the exhaust valve stems.
Oil consumption depends on oil viscosity, oil quality and driving conditions.
Oil consumption increases at high driving speeds and during frequent acceleration.
A new engine consumes more oil because the pistons and rings are breaking in against the cylinder walls.
Normal oil consumption is no more than 1 L per 1000 km.
When checking the oil level, note that due to oil dilution the true level is difficult to determine.
For example, if the vehicle is driven on repeated short trips and oil consumption is normal, after 1000 km or more the dipstick may show no drop in level at all. This is because the oil is gradually diluted by fuel or moisture, creating the impression that there is no oil consumption.
If the vehicle is then driven at high speed, the diluting components evaporate intensively, creating the impression that oil consumption is above normal.