**Abstract**

Biodiesel is one of the environment-friendly alternative fuels need to be developed in order to meet the increasing demand for mineral fuels for transportation. In this study, nonedible crude Mahua oil has been used to extract biodiesel. Performance, emission and combustion characteristics of Mahua oil biodiesel blends with conventional diesel are compared on a single cylinder, natural aspirated, water-cooled direct injection (DI) diesel engine. Brake thermal efficiency of an engine fuelled with Mahua biodiesel blend B30 has been shown nearly same or insignificant lower compare to mineral diesel. The optimum engine operating condition based on lower brake specific fuel consumption and higher brake thermal efficiency was observed at 60% load for blend B30 of crude Mahua oil biodiesel. From an emissions point of view blend, B30 was found to be the best fuel as it showed lesser exhaust emission such as CO, HC, CO2, and NOx. Heat and pressure curve with respect to crank angle showed the details of combustion characteristics and revealed that combustion starts earlier for higher biodiesel blends. Results show that biodiesel obtained from nonedible Mahua oil gave better results and can be used as an excellent substitute for fossil fuels.

**Keywords:** High FFA crude Mahua oil, transesterification, esterification, diesel engine, performance, emissions, combustion
