In order to compensate the energy demand and replacement of fossil fuels at least to some extent, the development of alternative energy sources is evitable. Global warming and waste management policies have forced for the use of alternative fuels on engines. The production of fuel from plastic wastes will indeed tackle the environmental pollution problem of waste plastic management in the landfills. Plastics being derived from petrochemical source has higher amount of hydrocarbon which yield oil with high calorific value. Engine tests have been carried out using neat Waste Plastic Oil and blends of Waste Plastic Oil in proportions of 25%, 50%, and 75% with diesel as fuel. Combinatorial Mathematics Based Approach (CMBA) has been adapted to choose the optimum blend for superior performance of the engine. CHNS (Carbon Hydrogen Nitrogen Sulphur) analysis of WPO blends reveals that the amount of oxygen increases with increase in WPO percentage in blends. NOx emission is higher for WPO blends than diesel. The results of CMBA and experimental tests showed that WPO25 is the optimum blend.