The piston is a reciprocating mechanism in the cylinder block of an automobile engine. The basic structure of the piston can be divided into a top, a head and a skirt. The top of the piston is the main part of the combustion chamber and its shape is related to the type of combustion chamber chosen. Gasoline engines mostly use flat-topped pistons, which have the advantage of a small heat absorption area. Diesel piston tops often have a variety of dimples, the specific shape, location and size of which must be compatible with the diesel engine's gas mixture formation and combustion requirements.