The oil pan is attached to the bottom of the engine with bolts and is the reservoir for oil that gets pumped throughout the engine to lubricate, clean and cool moving parts. A pump forces the oil from the pan through a filter to remove dirt and other debris before it circulates through the engine.
The pan is usually made of steel or aluminium and typically holds from four to six quarts of oil, depending on the engine. The oil dipstick extends into the oil pan and measures the oil level in the reservoir.
A drain plug on the bottom can be removed to drain oil. Oil leaks are common on engines as they accumulate miles, and oil pans can be one source of leaks or seepage. Gaskets or seals installed where the pan attaches to the engine block may wear out and allow leaks.
Drain plugs can leak if they are over-tightened or, in some cases, if washers aren’t replaced when the oil is changed. Pans also can be damaged when a vehicle goes off-road (whether intentionally or by accident) and hits a rock or other hard object.