In this study, the potential possibility of bioenergy was investigated as an alternative fuel for a naturally aspirated indirect injection diesel engine. The smoke emission of biodiesel fuel was reduced remarkably in comparison with diesel fuel, that is, it was reduced approximately 64% at 2500rpm, full load condition. And, power, torque and brake specific energy consumption showed no significant differences. However, NOx emission of biodiesel fuel was slightly increased compared with the commercial diesel fuel.