Biomass based alternative fuels are gaining more importance in the recent years because of their reduced emission profile. In the present investigation used palm oil collected from various restaurants of Tirunelveli region of India was blended with diesel fuel and butanol in varying proportions and the effect of these blends on fuel properties and diesel engine performance, emission and combustion were studied and were compared with the diesel fuel. The fuel properties of the blends were found to be better than used palm oil. Engine tests were carried out in a constant speed (1500 rpm) DI diesel engine by varying loads from 0% to 100%. Brake specific fuel consumption (BSFC) and brake thermal efficiency (BTE) of the blends were found to be lower than diesel fuel. Brake thermal efficiency of the blends increased with increasing butanol content in the blends. CO, NOx emissions and smoke opacity of the blends decreased with increasing butanol content and were found to be lower than diesel fuel. CO2 in the exhaust for the blends containing butanol was found to be lower than the values reported with diesel fuel. HC emission of the blends containing butanol was found to be higher than diesel fuel. The blends containing butanol produced higher heat release rate than diesel fuel. Ignition delay increased with the increasing butanol content in the blends. The blend 50%D-35%UP0-15%B showed better emission, combustion and performance characteristics. (C) 2013 Elsevier Ltd. All rights reserved.