The Engine's Lubrication System
At the heart of the engine's lubrication system is the oil pump. It creates the oil pressure to lubricate, clean, and cool the engine. Without this oil, the engine's valvetrain, bearings, and moving parts will fail.
The oil pump pickup screen filters large pieces, and the oil filter filters finer particles as small as 10-20 microns. The oil galleries are small holes drilled or cast into the engine block and heads that transfer the oil to the crankshaft, camshaft, and valve train.
A film of oil protects valve train components from wear. Low oil pressure causes a ticking sound from metal to metal contact in the valve train. The valve train will become noisy and soon fail without the necessary oil.
Drain holes in the cylinder head and block provide a return path to the sump. A restriction in the oil drainage system leads to puddling and premature valve seal failure.
The crankshaft bearings receive oil from the oil galleries. They ride on a thin film (~.001") of oil supplied through the oil supply hole. In addition, the crankshaft contains oil supply passages that transfer oil under pressure to the connecting rod journals/bearings. A restriction in the crankshaft oil passages leads to premature connecting rod bearing failure.