Dry sump

A dry sump system is a method to manage the lubricating motor oil in four-stroke and large two-stroke reciprocating internal combustion engines. The dry sump system uses two or more oil pumps and a separate oil reservoir, as opposed to a conventional wet sump system, which uses only the main sump (U.S.: oil pan) below the engine and a single pump. A dry sump engine requires a pressure relief valve to regulate negative pressure inside the engine so that internal seals are not inverted.

Dry sump lubrication is common on larger diesel engines such as those used in ships, as well as gasoline engines used in racing cars, aerobatic aircraft, high-performance personal watercraft, and motorcycles. Dry sumps may be chosen for these applications due to increased reliability, oil capacity, reduction of oil starvation under high g-loads, and/or other technical or performance reasons. Dry sumps may not be suitable for all applications due to increased cost, complexity, and/or bulk, among other factors.