All rotating components in a car’s engine are fitted with engine bearings. Their main role is to reduce friction between moving parts.
Different types of engine bearings fulfill different roles.
The main crankshaft bearings are mounted in the crankcase. They support the rotation of the crankshaft.
Connecting rod bearings maintain the movement of the crank pins within the connecting rods.
Camshaft bearings support the rotation of the camshaft, enabling the activation of the push rods and rocker arms to open and close the valves.
 
An engine bearing consists of flat cylinders, each of which consists of two halves, known as shells. The half shell design allows for a layer of oil to form on the surface of the bearing.
This lubricated surface helps dissipate heat, and protects the engine housing and rotating shaft from excessive wear.