Exhaust gas heat recovery proved to be one of the most effective ways to improve the efficiency of internal combustion engine. In this paper, a waste heat recovery system is designed using Engineering Equation Solver (EES) based on single stage Rankine and Organic Cycles. The heat from exhaust gas is used to heat up a pressurized working fluid, which is used to run turbine to produce additional power. The design of the system is modified to run different working fluids to maximize efficiency and part load performances. The results are used to determine suitable working fluid for a specific engine operation. Aim of this paper is to design a heat recovery system that is compatible with the operating range of the engine. The size of the heat exchangers are also compared for different working fluids. This paper provides a brief review of the benefits of using specific working fluid and the size of the heat exchanger required for the operation of a 26 kW engine. Assessment will provide the simulation results of the systems designed with different working fluids such as water, R113 and R125 for various operations of engine like part load and full load. The results of the simulation show that water is the best fluid to recover heat from the exhaust gas giving a power improvement of 14%, but it cannot be used for low load operations. In such cases R113 can be used to replace water which provides a power improvement of 8% whereas R124 gives an improvement of 2% at the lowest load and 4% at full load operation. The conclusion of this paper will provide an insight on efficient and compatible way of heat recovery in the application of various operations of engines.