Field tests for a variety of fuels on different tractor engines were carried out during the summers of 1981 through 1986. Fuels tested included alkali refined and winterized sunflower oil blended with diesel fuel, crude degummed sunflower oil blended with diesel fuel, high oleic safflower oil blended with diesel fuel, methylester of sunflower oil, or soybean oil. Blends of either 25% vegetable oil and 75% diesel fuel or 50% vegetable oil and 50% diesel fuel were used. Methylesters were not blended with diesel fuel. The manufacturers that participated in the project were John Deere, J.I. Case and Allis Chalmers.The project indicated that farm diesel tractors can be operated on any of the fuels that were tested. Care should be taken, however, since some signs of premature engine problems were observed. In general, continued use of these fuels cannot be recommended at this time. Under conditions where emergency fuel shortages develop, these sunflower oil fuels may enable farmers to complete field work and economically maintain their operations even though engine life is reduced.