The significance of this study is the complete replacement of diesel fuel with bio-fuels. For this purpose; bio-fuels, namely, methyl ester of paradise oil and eucalyptus oil were chosen and used as fuel in the form of blends. Various proportions of paradise oil and eucalyptus oil are prepared on a volume basis and used as fuels in a single cylinder, four-stroke DI diesel engine, to study the performance and emission characteristics of these fuels. In the present investigation a methyl ester derived from paradise oil is considered as an ignition improver. The results show a 49% reduction in smoke, 34.5% reduction in HC emissions and a 37% reduction in CO emissions for the Me50-Eu50 blend with a 2.7% increase in NO(x) emission at full load. There was a 2.4% increase in brake thermal efficiency for the Me50-Eu50 blend at full load. The combustion characteristics of Me50-Eu50 blend are comparable with those of diesel. (C) 2008 Elsevier Ltd. All rights reserved.