Petroleum fuels are being used exhaustively and are at the risk of depletion in the near future. This has led to extensive research for alternative Bio-fuels. In this context animal fats and edible oils are becoming very important. Their properties compare favorably with the requirement for running C.I. Engines after suitable conditioning. In this study of potential animal fats and vegetable oils, such as Fish Oil and Corn Seed Oil, tests have been carried out in terms of performance, combustion and emission characteristics of the Engine. Test runs reveal that these conditioned Bio-fuels perform well in running a Diesel engine.