The oil pan, or sump, in the MAN L21/31 engine (estimated code H21420) serves as the reservoir for engine lubricating oil. It collects and stores the oil as it circulates through the engine, ensuring vital components remain properly lubricated to reduce friction and wear. Made from durable materials to withstand thermal stresses and mechanical impacts, the oil pan is essential for maintaining engine longevity and optimal performance by facilitating efficient oil circulation and cooling.