The objective of this work was to analyze the practical potential of Methyl Ester of Jatropha oil (MEJ) on the basis of combustion, Performance and Emission in a single cylinder constant speed compression ignition engine. This study is based on the comparison of Diesel and Blends of 25, 50, 75, 100% (By Volume) of Methyl Esters of Jatropha oil (MEJ).This detailed analysis takes into account of some of the Combustion and performance parameters such as ignition delay, combustion duration, Rate of heat release, cumulative heat release, Peak Flame Temperature and Pressure, work done, Efficiency, Specific fuel Consumption and emissions characteristics such as HC, CO, NOX and Smoke. In the final analysis it was found that, the Blends of Methyl Ester of Jatropha oil (MEJ) is a viable alternate fuel for diesel engines.