In this study, palm oil fatty acids which were obtained from crude glycerin by neutralization were used for biodiesel production. The crude glycerin is a by-product of a biodiesel production process. Mixtures of the biodiesel with diesel fuel were tested in an unmodified direct injection diesel engine at full load condition. In general, specific fuel consumption of biodiesel fuels increased depending on the amount of biodiesel in the test fuels. CO emission and smoke opacity decreased up to 40.87 and 23.69%, respectively. NOx emissions increased up to 12.36%. CO2 emission showed a trend of decreasing with biodiesel fuel.