A device used to remove oil from the air discharged from an oil-lubricated air pump. A wet, vane-type air pump is lubricated and sealed by a small amount of engine oil flowing through the pump. This oil must be removed before the air can be used.

An oil separator contains a series of baffles over which the pump-discharge air must pass. Any oil in the air sticks to the baffles and drains to the bottom of the separator housing, and from here it is returned to the engine crankcase. Air from which the oil has been removed leaves the separator from a connexion above and beyond the baffles.