The main oil way:
The oil is drew from the oil pan through the oil strainer to the oil pump, then passes the oil filter and enters the main oil gallery in the cylinder block. If the oil pressure is too high, the relief valve will be pushed open to allow the oil to flow back to the oil pan. If the oil filter is clogged by impurities, the oil will enter the main gallery through the bypass valve without filtered.
1-bypass valve 2-oil pump 3-oil strainer 4-oil pan 5-drain plug 6-relief valve 7-oil filter 8-main oil gallery 9-oil passages 10-crankshaft 11-OPS 12-oil pressure light
The oil way is divided into two roads in the main oil gallery.
Oilway to the crank mechanism
The oil from the main gallery arrives to the main bearings through the oil passages in the cylinder block, then reaches the connecting rod bearings throught oil passages in the crankshaft. At the same time, the rotating connecting rod bearings will dip into the oil pan, and splashing the oil to piston pins, cylinder walls, and piston rings. Then the oil flows back to the oil pan.
Oilway to the valve train
The oil from the main gallery arrives to the camshaft bearings through the oilway in the cylinder head, and then to rocker arms and vavles. Finally, it goes back to the oil pan, too.
Modern cars have a oil pressure switch(OPS), so there is a small oilway to the OPS.
The complete oil circuit is below:
