Six Stroke engine, the name itself indicates a cycle of six strokes out of which two are useful power strokes. According to its mechanical design, the six-stroke engine with external and internal combustion and double flow is similar to the actual internal reciprocating combustion engine. However, it differentiates itself entirely, due to its thermodynamic cycle and a modified cylinder head with two supplementary chambers: combustion and an air heating chamber, both independent from the cylinder. In this, the cylinder and the combustion chamber are separated which gives more freedom for design analysis. In addition to the two valves in the four-stroke engine, two more valves are incorporated which are operated by a piston arrangement. The Six Stroke is thermodynamically more efficient because the change in volume of the power stroke is greater than the intake stroke and the compression stroke. The main advantages of six stroke engine include a reduction in fuel consumption by 40%, two power strokes in the six-stroke cycle, a dramatic reduction in pollution, adaptability to multi-fuel operation. Six-stroke engine’s adoption by the automobile industry would have a tremendous impact on the environment and world economy. There are additional two strokes, namely another power, and exhaust strokes. The engine works by harnessing wasted heat energy created by the fuel combustion. After the combustion stage water is injected into the superheated cylinder. The water explodes into steam and forces the piston down. It, in turn, helps to cool the engine. That resulted in normal levels of power but using much less fuel. It also has the advantage of not requiring an external cooling system. In order to achieve these benefits, major modifications of conventional internal combustion engine must be done. In this paper, the modification of the conventional four-stroke internal combustion engine is illustrated to convert it into six stroke engine.