General information about the lubrication system (Audi A4 B6)

The engines are equipped with a pressure circulating lubrication system.

The oil pump sucks oil through a mesh from the oil pan and supplies it under pressure to the system through the oil filter. At the outlet of the oil pump there is a pressure reducing valve. When the pressure increases above the set value, the valve opens and some of the oil drains back into the oil pan.

The oil filter's central opening allows oil to flow directly into the main channel. When the oil filter becomes clogged, a bypass valve directs unfiltered oil into the system.

The main oil line branches off into channels for lubricating the crankshaft bearings. Oil is supplied to the connecting rod bearings through inclined holes in the crankshaft. To cool the pistons, oil is injected onto them from below through nozzles.

At the same time, oil reaches the cylinder heads through vertical galleries and is used to lubricate the camshaft bearings and valve train components of the gas distribution system.

Depending on the engine power, the oil can be cooled in an additional oil cooler located on the side, near the oil filter housing and included in the engine cooling system circuit.