There is problem of cylinder wear in I.C. engine and this is solved by use of cylinder liners. Cylinder liners are in the form of barrels made of special alloy iron containing silicon, manganese, nickel and chromium. They are cast centrifugally. It is now customary to fit cylinder liners on engines of cars and commercial vehicles. These liners are of the oil hardening type and offer considerably longer life for the engine. 

The cylinder liners are of two types:

1. Dry liners - Dry liner is made in the shape of barrel having a flange at the top which keeps it into position in the cylinder block. The entire outer surface of the dry liner bears against the cylinder block casting and hence has to be machined very accurately from the outside also. Thus it is not in direct contact with the cooling water and hence is known as dry liner. Its thickness ranges from 1.5mm to 3mm. It is used mostly for reconditioning warm cylinders.

2. Wet liners - A Wet liner forms a complete cylinder barrel. It is provided with a flange at the top which fits into the groove in the cylinder block. At the bottom either the block or the liner is provided with grooves, generally three in numbers, in which the packing rings made of rubber are inserted. The liner is in direct contact with the cooling water and hence is known as wet liner. The outer surface of the liner does not require accurate machining. Wet liners are thicker than dry liners, ranging from 1.5mm to 6mm.