An alternative fuel to solar used in diesel engines was prepared from sunflower oil. Since the oil was too viscous to be used efficiently as fuel, it was chemically modified to reduce its viscosity. Chemical modification of the oil was made by catalyzed esterification with short chain alcohols being methyl and ethyl alcohols. The modified products were then evaluated according to their fuel properties as compared to diesel fuel. The fuel properties considered were viscosity, pour point, calorific value, flash point, and cetane number in addition to some other properties.In addition, the performance of a diesel engine was tested when fueled with a 50% blend of diesel oil and the oil methyl ester, a 50% blend of diesel oil and the oil ethyl ester, and when fueled with diesel oil. The tested parameters were the brake-specific fuel consumption and brake thermal efficiency. The results of engine testing have proved that the engine performance was best using a 50% blend of diesel oil and the oil methyl ester. The brake-specific fuel consumption using this blend was 0.24 kg/BHp compared to 0.26 kg/BHp using diesel oil. The brake thermal efficiency using that oil blend was 37.6% compared to 31% with diesel oil.