In a medium speed engines heavy fuel oil burns using higher injection pressure and within short injection timing. The compression pressure and temperature are also high. In ideal condition the fuel is burnt by disintegration of complex hydrocarbon of HFO in high temperature pack of compressed air to lighter hydrocarbon which evaporates and burns in vapour state.
The product of fuel oil are yet to be burnt reach the cylinder surface through clearence space between the piston and liner. A reaction is started with cylinder lub oil forming a resinous compound lacquer. Build up of lacquer on honed liner surface and at places where temperature of liner is low initiates formation of more resinous substance through a process of POLYMERIZATION. Such deposit sticking on liner surface have resulted back polishing of liner forming at the same time a glazed surface. The liner wears out as the deposits become hard when more volatile part of it is evaporated by rubbing action of piston rings.