In this study, use of sunflower oil methyl ester as an alternative fuel in a 4 stroke turbo diesel engine with 4 cylinders, direct injection, and 55 kW power was analyzed. The engine has been fueled by diesel fuel and biodiesel (B100) obtained from methyl ester of sunflower oil and by running the test engine with 14 different speeds and full load, the results have been analyzed. Smoke emissions obtained in biodiesel use were slightly less, which could be attributed to better combustion efficiency. Also, HC and CO emissions of biodiesel were found to be lower. Results of this study show that performance values of sunflower oil methyl ester are similar to those of diesel fuel. It can be concluded that biodiesel's exhaust emissions are lower than diesel fuels, which indicates that biodiesel has more favorable effects on air quality.