The world is on brink of energy crisis. The limited fossil fuel sources are unable for the continuously increasing demand of energy. This associated with increasing price of fossil fuels and the awareness of the impacts of environmental pollution and global warming, has forced a search for an alternative source of energy, which is the renewable, and safe and non-polluting‥ In the present experimental research work, used vegetable oil methyl ester (UVOME) is derived through transesterification of used vegetable oil using methanol in the presence of sodium hydroxide (NaOH) catalyst. Experimental investigations have been carried out to examine the combustion characteristics in a direct injection transportation diesel engine running with diesel, biodiesel (UVOME), and its blends with diesel such as B20 and B80. Acareful analysis of the crank angle at which cylinder pressure rise and heat release occurs was carried out. The emission performance of diesel engine using diesel fuel and bio-diesel fuel are compared. The result has shown that biodiesel has comparable performance and lower brake specific fuel consumption than diesel with significant reduction in emissions of CO, hydrocarbons (HC), but slightly increased NOx emissions.