Oil Circulation Circuit Diagram

BMW engines use pressure lubrication. The oil pump draws oil from the oil pan through a strainer and forces it under pressure into the system through the oil filter. Filtered oil flows through the centre of the filter element into the main oil gallery. If the filter is clogged, oil bypasses the filter through the bypass valve and enters the system unfiltered.

A pressure regulating valve is installed after the oil filter and maintains a pressure of approximately 4 bar. When oil pressure rises, the valve opens and returns oil to the oil pan.

Branches from the main gallery supply the crankshaft main bearings. Through angled drillings, oil is fed to the connecting rod bearings and from there to the piston crowns and cylinder walls.

At the same time, engine oil is fed through vertical tubes into the cylinder head, lubricating the camshaft bearings, hydraulic valve lash adjusters and valve guides. Restrictor passages supply the required amount of oil to the above components in the cylinder head.

In addition, oil is supplied to the timing chain and its tensioner and, on petrol engines, to the oil pump drive chain.