A naturally aspirated multi cylinder diesel genset (DG) was operated successfully with mixed fuels (fossil-diesel (M), refined rice bran oil (RRBO) and producer gas from a wood gasifier). Performance of DG set in FD, dual fuel mode (FD + RRBO in different proportion and FD + producer gas) and mixed fuels mode (with preheated blend of 75% RRBO + FD and producer gas) at different engine load conditions are presented in this paper. Performance of DG was evaluated in terms of specific energy consumption (SEC), brake thermal efficiency, exhaust gas temperature and exhaust gas composition. Study revealed that blends containing up to 75% RRBO with FD could be used as engine fuel without any adverse effect on the engine. The blend of RRBO and FD was preheated to 60 degrees C before use in the compression ignition (CI) engine. In general, exhaust gas temperature and SEC increased in all the three modes compared to FD. However, break thermal efficiency decreased. It may be due to lower calorific value of RRBO and producer gas. It was observed that at 84% engine load having 18.4:1 compression ratio (CR) and operating in dual fuel mode (FD + producer gas), the concentration of pollutants like carbon monoxide (CO), carbon dioxide (CO2 nitric oxide (NO), nitrogen dioxide (NO2) reduced by 55%, 19.7%, 82% and 83%, respectively, while hydrocarbon (HC) increased by 67.2% as compared to FD. Similarly at 84% engine load having 17:1 CR and operating in dual fuel mode (FD + RRBO), the concentration of pollutant like CO, CO2 and HC reduced by 60%, 0.86% and 91%, respectively. However, NOx increased by 23.48% as compared to FD. In mixed fuel mode (preheated blends of RRBO + FD in the proportion of 3:1 and producer gas) at 84% engine load having 18.4:1 CR, the concentration of pollutants like HC, NO and NO2 reduced by 48.28%, 61.57% and 80.48%, respectively, while CO increased by 16.31% as compared to FD. In addition to the findings on environmental aspects, the study also proved that the diesel engine could be run safely in mixed fuel mode (53% producer gas, rest RRBO and FD at the ratio of 3:1 and heated at 60 degrees C). (c) 2006 Elsevier Ltd. All rights reserved.