The performance and exhaust emissions of a direct injection turbocharged tractor diesel engine were optimized by running the engine on a vegetable oil pressed from mustard seeds.The unesterized mustard seed oil (MSO) was cleaned just letting it stand and clear. Injection timing of the engine was varied to identify optimum timing. No other modifications were made to the engine.An injection advance of 17° proved to be the optimum when running on MSO, as the engine generated a brake torque with MSO almost equal to that achieved with a diesel engine. The brake thermal efficiencies (BTE) were rather similar, and use of the retarded timing further reduced NOx emissions.Exhaust HC emissions were determined using FT-IR technology. Generally, the contents of measured HC species were higher with diesel fuel than with MSO.Most of the field observations from four harvesting seasons proved encouraging.