Classification I.C. Engines Type of the fuel used as Petrol engine Diesel engine Gas engine Bi-fuel engine Nature of thermodynamic cycle as Otto cycle engine Diesel cycle engine Duel or mixed cycle engine Number of strokes per cycle as Four stroke engine Two stroke engine Method of ignition as Spark ignition engine (S.I. engine)-mixture of air and fuel is ignited by electric spark. Compression ignition engine (C.I. engine)- fuel is ignited with hot compressed air. Method of cooling as Air cooled engine Water cooled engine Speed of the engine as Low speed Medium speed High speed Petrol engine are high speed engines and diesel engines are low to medium speed engines. Number of cylinder as Single cylinder engine Multi cylinder engine Position of the cylinder as Inline engines V – engines Radial engines Opposed cylinder engine