Fossil fuel resources are decreasing daily and attracted researchers to focus on alternative fuels. Biofuels (renewable fuels) are attracting attention worldwide as blending components or direct replacements for petroleum based fuel in vehicle engines. Moreover, Biofuel will also provide rich biomass and nutrients to the soil. This paper presents the results of performance and emission analysis carried out in a naturally aspirated unmodified diesel engine fuelled with preheated crude palm oil (PCPO) and its blends with diesel. It was observed that preheated CPO reduces exhaust emissions such as CO and HC as compared to ordinary diesel (OD). This is mainly attributed to the fact that preheating of crude palm oil reduces its viscosity to the level of ordinary diesel fuel, which improves the fuel spray and atomization characteristics and produces better combustion.