In the present work Jatropha biodiesel has been proposed as an alternative fuel for powering existing diesel engine. Transesterification has been carried out for effective utilization of Jatropha oil. Thermal efficiency, brake specific fuel consumption(BSFC),smoke opacity, exhaust gas temperature(EGT),brake mean effective pressure(BMEP) have been measured for Jatropha oil. A comparable study is carried out on the basis of different performance curves, which are plotted for each proportion between thermal efficiency versus brake mean effective pressure(BMEP), smoke opacity versus brake mean effective pressure(BMEP) and brake specific fuel consumption (BSFC) versus brake mean effective pressure(BMEP). Transesterification process is a very effective process for reducing high viscosity of vegetable oils and bringing about changes at molecular level. Vegetable oils do not exhibit combustion related problems and the transesterification process produces a Bio-origin fuel that behaves almost like mineral diesel oil.