The world is facing crisis due to the dwindling sources of fossil fuels. Rapid depletion of conventional energy is a matter of serious concern for the mankind. There is a necessity to find alternative fuels for different industrial needs, automobiles and aircrafts. The conventional forms of energy supply and consumption are causing serious economical as well as environmental problems. Import dependence for oil in India is about 70 percent, and is likely to increase further. If the fossil fuels

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... re consumed at present rate it may not take much time before the oil reserves get totally exhausted. It is, therefore, imperative to search for the alternative fuels that are renewable in nature, locally grown and friendly to environm1ent. Diesel and alternative fuels like coconut oil and cotton seed oil are used as fuels. Previously efficiency of alternative fuels like coconut oil and cotton seed oil blends with diesel was tested. The blends of varying proportions of these alternative fuels and diesel are used to run the engine and significant improvements in engine performance and emission characteristics are observed.These improvements are attributed to more complete combustion of oxygenated fuel. Engine performance values such as Indicated Horse Power, Brake Horse Power, Fuel Consumption, Mechanical Efficiency, Volumetric Efficiency, Indicated Brake Thermal Efficiency and Air Fuel Ratios are determined by varying fuel injection pressure with variation of Engine loads along with different blends of oils. Even through the viscosity of the coconut oil is low and is economically friendly. Considering the thermal efficiency, the cotton seed oil blend (B50) is preferable as it is giving it is good characteristics curve.