As Conventional fuels are going to deplete soon, we need a alternative fuel. Bio-diesel is such a renewable alternative fuel. Many studies conducted on biodiesel showed that biodiesel blending with diesel up to 20% can give good performance and emission characteristics on diesel engines, the drawback is the higher NOx emission. Here we are blending rubber seed and jatropha biodiesel with diesel to improve its properties we are adding cetane improver 2- ethyl hexyl. Results of the experiment on a V C R engine so the optimum compression ratio for a diesel engine can also be determined from our...