Nowadays, natural-based oxygenated fuels, especially biodiesel and ethanol, have been considered as substitutes for fossil fuels. Because of relatively lower energy content of oxygenated fuels, it is necessary to blend them with fossil ones. In this research, authors conducted an investigation on some BED blends to determine and compare their effects on equivalence ratio, exhaust oxygen fraction and water and oil temperature in a diesel engine. For this purpose, 18 different blendes of ethanol and biodiesel with net diesel fuel were tested in a MT4-244 engine(1) considering two engine speeds in full load condition. In almost all samples the equivalence ratio decreased with increasing of biodiesel and ethanol percents. Exhaust oxygen fraction in all of samples increased with increasing of biodiesel and ethanol percents, whereas the engine water and oil temperatures slightly reduced. (C) 2011 Elsevier Ltd. All rights reserved.