Wet sump

A wet sump is a lubricating oil management design for piston engines which uses the crankcase as a built-in reservoir for oil, as opposed to an external or secondary reservoir used in a dry sump design.

Piston engines are lubricated by oil which is pumped into various bearings, and thereafter allowed to drain to the base of the engine under gravity. In most production automobiles and motorcycles, which use a wet sump system, the oil is collected in a 3 to 10 litres (0.66 to 2.20 imp gal; 0.79 to 2.64 US gal) capacity pan at the base of the engine, known as the sump or oil pan, where it is pumped back up to the bearings by the oil pump, internal to the engine.