The performance of Ricardo E6 engine using biodiesel obtained from mahua oil (B100) and its blend with high speed diesel (HSD) at varying compression ratio (CR), injection timing (IT) and engine loading (L) has been presented in this paper. The brake specific fuel consumption (BSFC) and exhaust gas temperature (EGT) increased, whereas brake thermal efficiency (BTE) decreased with increase in the proportion of biodiesel in the blends at all compression ratios (18:1-20:1) and injection timings (35-45 degrees before TDC) tested. However, a reverse trend for these parameters was observed with increase in the CR and advancement of IT. The BSFC of B100 and its blends with high speed diesel reduced, whereas BTE and EGT increased with the increase in L for the range of CR and IT tested. The differences of BTEs between HSD and B100 were also not statistically significant at engine settings of 'CR201T40' and 'CR201T45'. Thus, even B100 could be used on the Ricardo engine at these settings without affecting the performance obtained using HSD. (c) 2008 Elsevier Ltd. All rights reserved.