The oil separator prevents the oil or oil mist to escape from the crankshaft casing and is therefore a part of the ventilation system of the crankshaft casing.

It is fitted with a filter that catches the oil particles out of the air and drains it back into the engine. The oil separator also handles the pressure management of the crankshaft-casing and is mandatory to meet modern emission standards.

When the oil separator is defective, the engine will have a higher oil consumption and emission.

In normal use the oil filter will slowly catch oil impurities and eventually get stuck.

Before the oil separator gets stuck it should be exchanged to ensure the proper crankshaft-casing ventilation.