This work investigated the effects of induction of hydrogen and oxygen mixture (H-2/O-2) to a heavy-duty diesel engine (HDDE) on the thermal performance, fuel consumption and emission characteristics. The HDDE was tested at one low load steady-state condition, 24.5% of the max load (40 km/h), using neat diesel and seven H-2/O-2 mixtures: 10-70 L/min, interval 10 L/min. The results show that brake thermal efficiency is increased from 31.1% for neat diesel to 39.9% for 70 L/min of H-2/O-2 mixture. For 10-40 L/min of H-2/O-2 mixture addition, the brake specific fuel consumption (BSFC) was higher than that of neat diesel. However, for 50, 60 and 70 L/min of H-2/O-2 mixture addition, the BSFC was lower than that of neat diesel by about 3.2%, 9.9% and 10.5%, respectively. Due to improved combustion efficiency, the emission concentrations of hydrocarbon, carbon dioxide and carbon monoxide were all lowered, while those of the nitrogen oxides were increased. (C) 2011 Elsevier Ltd. All rights reserved.