The components and parts that provide oil pressure and distribute lubricating oil within the engine. Includes the plumbing leading to and from the using external systems and components which utilize engine system oil for operation. Does not include the externally mounted oil system storage tanks and connecting lines which are filed in JASC code 7910, or the oil cooler lines, hoses, and drain valves in JASC code 7920. Typical parts are pressure and scavenge pump, impeller, housing, filter, air-oil separator, crankcase breather, screen, element, relief valve, drive gear, adapter, pan, dipstick, cap, propeller governor oil lines, etc.