In this study, blends of soybean oil ethyl ester and diesel fuel are tested as alternative fuel in a single cylinder, air cooled pre-combustion chamber diesel engine at different speeds and their effects on engine performance and emissions are analyzed. It is observed that the average moment obtained by 5% soybean oil ethyl ester and diesel fuel blend (SOE5) is 0.53% lower, the level of power obtained is 1.8% lower; however, specific fuel consumption is approximately 4.31% higher than those of diesel fuel. In the experiments conducted with 20% soybean oil ethyl ester and diesel fuel blend (SOE20), it is observed that the average moment is 1.74% lower, the level of power obtained is 5.91% lower; however, specific fuel consumption is approximately 10.94% higher than those of diesel fuel. Moreover, while a distinctive decrease is observed in CO emissions of fuel blends, NOx emissions are obtained very close to that of diesel fuel.