The crude oil resources are depleting as the days progress and biodiesel is an emerging substitute. But the usage of biodiesel is associated with fuel atomization problems. The prime cause is the high viscous nature of oils obtained from green matter. As we know that with increase in temperature of oil viscosity decreases. Current work deliberates the influence of preheating of biofuel on the engine output parameters. DI diesel engine fuelled with preheated biofuel blends result in increase in thermal efficiency and drop in HC, CO emissions, but the rise in peak cylinder temperature resulted in increase in NO_x emissions.