Engine bearings both reduce friction between the rotating part of the engine and the stationary part while supporting the crankshaft.
The bearing material must be extremely strong because of the stresses caused by the explosions inside the internal combustion engine.
Engine bearings-Reducing friction is accomplished in part by the fact that dissimilar metals slide against each other with less friction and wear than similar materials will.
Without lubrication, engine bearings will quickly overheat and weld itself to the crankshaft. Therefore, engine bearings and cranks are designed so that the crank rides on an incredibly thin protective film of oil. Consequently, separating the crankshaft and the bearing surface from one another. This protective film is only generated while the shaft rotates, as the spinning crankshaft is the mechanism for oil dispersal.
As the oil is circulated throughout the engine via oil pump, it fills in the space between the bearing clearances, allowing the shaft rotation to pull oil in between the shaft and the bearing.