The change of intake oxygen content caused by altitude variation and the change of fuel oxygen content both affect the performance of diesel engines. In this paper, comparative experiments were performed on a high pressure common rail diesel engine fueled with pure diesel and biodiesel-ethanol-diesel (abbreviated as BED) blends with oxygen content of 2%, 2.5%, and 3.2% in mass percentage at different atmospheric pressures of 81 kPa, 90 kPa, and 100 kPa. Moreover, in order to study the effect of different fuel blends with the same oxygen content on the performance of the diesel engine, tests were conducted on the diesel engine fueled with the BED blend and a biodiesel-diesel (abbreviated as BD) blend at 81 kPa ambient pressure. The experimental results indicate that the influence of altitude variation on the full-load engine brake torque is not significant when the pure diesel fuel is used. With the increase of BED fuel oxygen content, the engine brake torque reduces. When the pure diesel fuel is used, with the increase of atmospheric pressure, the brake specific fuel consumption (BSFC) decreases. As the fuel oxygen content increases, there is no significant difference in brake specific fuel consumption of the BED blends. And the values of brake specific energy consumption (BSEC) gradually decrease. Soot emissions of the diesel engine decrease with the increase of atmospheric pressure and fuel oxygen content. The effect of soot emission reduction by increasing the oxygen content of the fuel is more significant than the effect of increasing atmospheric pressure. The effects of BD and BED fuels with basically the same oxygen content on the full-load performance, fuel economy, and soot emissions of the diesel engine are different. The BSFC and soot emissions of the BED fuel are lower than those of the BD fuel. (C) 2013 Published by Elsevier Ltd.