Short engine tests were used to determine the rate of carbon deposition on direct injection diesel nozzles. Winter rape, high‐oleic and high‐linoleic safflower blends with 50% diesel were tested for carbon deposit and compared to that with D‐2 Diesel Control Fuel. Deposits were greatest with the most unsaturated fuel, high‐linoleic safflower, and least with winter rape. All vegetable oil blends developed power similar to diesel fueled engines with a 6 to 8% greater fuel consumption.