There are no standard methods or ways of classifying I.C. Engines.

They may be classified in many ways such as following:

(1) Arrangement of Engine Cylinders:

(i) Horizontal engine

(ii) Vertical engine

(iii) V engine

(iv) In-line engine

(v) Opposed cylinder engine

(vi) Opposed piston engine

(vii) Deltic engine

(viii) Y engine

(ix) Radial engine

(2) Working Cycle Employed:

(i) Four stroke cycle engine

(ii) Two stroke cycle engine

(3) Fuel Used:

(i) Petrol engine

(ii) Diesel engine

(iii) Gas engine

(iv) Bi-fuel engine

(4) Nature of Thermodynamic Cycle Used:

(i) Otto cycle engine

(ii) Diesel cycle engine

(iii) Dual combustion cycle engine.

(5) Speed:

(i) Low speed engine

(ii) Medium speed engine

(iii) High speed engine

(6) Method of Cooling:

(i) Air cooled engine

(ii) Water cooled engine

(7) Field of Application:

(i) Stationary engine

(ii) Marine engine

(iii) Automobile engine

(iv) Motor-cycle engine

(v) Aero engine

(vi) Locomotive engine, etc.

(8) Method of Ignition:

(i) Compression ignition engine

(ii) Spark ignition engine.