The main function of compression ring is to seal the space between the piston and the liner. High pressure gases due to combustion enters behind the piston rings. This pushes the piston rings in the outward direction to have a good contact between liner and the piston rings. At the same time, piston rings are also pushed downwards on the piston ring landing grooves. Thus it forms a complete sealed space above the piston rings in between the liner and the piston. Hence the force of gas behind the piston rings which forces the piston rings outwards is of prime importance. If the piston rings are seized or the grooves are not clear i.e. it is obstructed with carbon, there is a possibility the piston rings will not have proper contact with the liner and blowpast will take place which will cause breaking of piston rings and scuffing. As the cylinder liner is better cooled off than the piston and in order to keep the piston and the piston rings in cooled condition to have better lubrication between piston rings and the liner, it is necessary that the piston rings should be kept as cool as possible. When the piston ring is in contact with the liner, some amount of heat from the piston is transmitted to the liner via the piston rings thus keeping the piston crown and the rings in cool condition, thus promoting the lubrication between the liner and the piston rings.