Today, a decrease in the reserves of fossil fuels and negative effects of these fuels on the environment has increased the interest in alternative energy sources. One of the alternative energy sources is biodiesel, which is made of vegetable oil. In this study, biodiesel has been produced from crude and refined soybean oil by using transesterification method. The effect of crude soybean methyl ester and refined soybean methyl ester on engine performance and emissions has been examined through a diesel engine with single cylinder and direct injection. While engine power and moment decrease when compared to the diesel fuel through use of crude soybean methyl ester and refined soybean methyl ester, there is an increase in relation to specific fuel consumption. When compared to the diesel fuel, through use of crude soybean methyl ester and refined soybean methyl ester, there is a decrease with regard to carbon monoxide emissions on average at a rate of 11.98 and 6.96%, respectively. While nitrogen oxide emissions decrease at a rate of 20.5% on average through use of crude soybean methyl ester, they increase by 20.1% when refined soybean methyl ester is used.