The main objective of the paper is the determination of energetic and pollution performance of a diesel engine fueled with three different fuels: diesel fuel, diesel fuel-animal fat blends and diesel fuel-animal fat–butanol blends. At the rise of animal fat percent in mixture with diesel fuel, the flow resistance of blend increases, because the fuel viscosity increase, the fuel atomization is worsened. Through butanol addition, the viscosity of the blend decreases and the engine operation is improved. The engine performance and the pollutant emissions level at the use of 5% and 10% animal fat in blends with diesel fuel, with or without addition of 5% butanol in content, are presented comparative to diesel fuelling. The indicated mean effective pressure, maximum pressure, maximum pressure rise rate, maximum rate of heat release, indicated specific energetic consumption, HC, NO_x and smoke emissions level of the diesel engine fuelled with butanol-animal fat-diesel fuel blends are evaluated and analyzed.