Oil line (BMW 7 Series E32)

BMW engines have a so-called circular pressure lubrication system. In this system, the oil pump sucks engine oil from the oil sump through a mesh filter and delivers it to the oil filter. Through the filter's central axis, the cleaned oil enters the main oil line. If the oil filter is clogged, a special valve directs unfiltered oil bypassing the oil filter directly into the main oil line. Behind the oil filter, the oil pressure at about 4 bar is regulated by an oil pressure reducing valve. At higher oil pressure, the valve opens and some of the oil flows back into the sump.

The main oil line has channels for lubricating the crankshaft bearings. Through oblique holes in the crankshaft, oil is supplied to the connecting rod bearings, and from there it is injected into the cylinder bores and onto the pistons.

At the same time, engine oil flows through vertical pipes into the cylinder head to lubricate the camshaft bearings (shafts), hydraulic valve lifters and valve guides. The backflow blocker ensures that there is always enough oil in the cylinder head to lubricate these parts.

In addition, oil is supplied to the timing chain(s) from the tensioners, and in gasoline engines, also to the oil pump drive chains.