Using hydrogen as an additive to enhance the conventional diesel engine performance has been investigated by several researchers and the outcomes are very promising. However, the problems associated with the production and storage of pure hydrogen currently limits the application of pure hydrogen in diesel engine operation. On-board hydrogen-oxygen generator, which produces H-2/O-2 mixture through electrolysis of water, has significant potential to overcome these problems. This paper focuses on evaluating the performance enhancement of a conventional diesel engine through the addition of H-2/O-2 mixture, generated through water electrolysis. The experimental works were carried out under constant speed with varying load and amount of H-2/O-2 mixture. Results show that by using 4.84%, 6.06%, and 6.12% total diesel equivalent of H-2/O-2 mixture the brake thermal efficiency increased from 32.0% to 34.6%, 32.9% to 35.8% and 34.7% to 36.3% at 19 kW, 22 kW and 28 kW, respectively. These resulted in 15.07%, 15.16% and 14.96% fuel savings. The emissions of HC, CO2 and CO decreased, whereas the NOx emission increased. (c) 2009 Elsevier Ltd. All rights reserved.