Crankcase: The upper crankcase and the cylinder block are cast as a whole, and the lower crankcase is used to store lubricating oil and close the upper crankcase, so it is also called the oil pan diagram. The oil pan is subjected to very little force and is generally stamped from thin steel plates, the shape of which depends on the general arrangement of the engine and the capacity of the oil. The oil pan is equipped with an oil stabilizing baffle to prevent the oil level from fluctuating too much when the car is jolting. The bottom of the oil pan is also equipped with an oil drain plug, which is usually equipped with a permanent magnet to adsorb metal chips in the lubricating oil and reduce the wear of the engine. A liner is installed between the joint surfaces of the upper and lower crankcases to prevent lubricating oil leakage.