The sump is bolted to the engine under the crankcase.
It is a reservoir, or storage container, for the engine lubricating oil, and a collector for oil returning from the engine lubricating system.
The sump can be formed as a thin sheet metal pressing, and shaped to ensure that oil will return to its deepest section. The oil pickup tube and strainer are located in this deep section to ensure they stay submerged in oil, and to prevent air being drawn into the oil pump.
Some high performance vehicles have a windage tray fitted to prevent churning of the oil by the rotation of the crankshaft.
Baffles prevent oil from surging away from the pickup during cornering, braking and accelerating.
The sump’s large external surface area helps heat transfer from the oil to the outside air.
In some designs, the sump is an aluminum alloy casting with fins and ribs to assist in this heat transfer.