Engine oil circuit (Audi A6 C5)

The engine is lubricated under pressure. The oil pump takes oil from the oil pan through a mesh filter and delivers it under pressure through a fine oil filter. The oil pump has a bypass valve that maintains the pressure at one level in the engine lubrication system. If the pressure in the engine lubrication system rises above a certain level, the bypass valve opens and some of the oil flows back into the oil pan.

After passing through the oil filter, the purified oil enters the main oil line. The oil line contains an oil pressure sensor, which lights up the control lamp on the instrument cluster to indicate low oil pressure. The oil filter contains a valve that, if the oil filter is heavily contaminated, bypasses the uncleaned oil directly into the oil line.

From the main line, oil is supplied under pressure through channels to lubricate the main bearings of the crankshaft and then through channels in the crankshaft to the connecting rod bearings. To cool the pistons, oil is sprayed through nozzles onto the lower part of the pistons.

Oil is supplied through the channels to the cylinder head to lubricate the camshaft bearings and to the hydraulic tappets.