A comparative analysis of performance and emission of five non-edible vegetable oils (Nerium oil, Jatropha, Pongamia, Mahua and Neem oils) blends with diesel of different proportions has revealed that Nerium oil has better performance and emission characteristics, compared to esters of Jatropha, Pongamia, Mahua and Neem oils. Without compromising the engine performance, the Nerium blend can be used in existing diesel engines. It is scientifically established that a blended diesel fuel (comprising 20% of biodiesel and 80% of diesel) gives optimum performance on the conventional diesel engine. Obviating any engine modifications, biodiesel can easily operate in a compression-ignition (diesel) engine while vegetable and waste oils operate only in fuel converted diesel engines. The use of biodiesel in conventional diesel engines steeply reduces the emission of major pollutants like unburned hydrocarbons (HCs), carbon monoxide (CO) and particulate matters. Non-edible oils obtained from plant Species: karanj, Jatropha, Manual, Neem (Azadirachta Indica) can be used as a Biodiesel. As compared to biodiesel and fossil diesel, Neat vegetable oil which can grow in a rural area easily has the highest potential of reducing greenhouse gas emissions.