A durability test was performed with a direct injection turbocharged, intercooled tractor diesel engine, fueled with a vegetable oil pressed from mustard seeds.The unesterized mustard seed oil (MSO) was cleaned by simply letting it stand and clear. A charge air cooler was installed in the engine. Basic performance and exhaust emissions were first determined by operating the engine on diesel fuel oil (DFO). Thereafter, the same measurements were made with MSO as fuel.At the third stage, the engine was operated for 150 hours according to a standard loading cycle using MSO as fuel. After this running period, performance and exhaust emissions were again measured.The results showed that the rated power had decreased somewhat during the period. The maximum torque and brake thermal efficiencies, however, were very similar to that observed before the test. The CO emissions were higher at some low loads, but the exhaust smoke had been reduced. Oxides of nitrogen increased at the intermediate speed. Some hydrocarbon species increased, while others were reduced.Consumption of potassium hydroxide of the lubricating oil increased during both running periods.