Four John Deere and two J.I. Case tractors were fueled with 25% or 50% blends of alkali-refined, winterized sunflower oil and No. 2 diesel fuel while in farm service. All engines were turbocharged, direct injection diesel engines and each was operated for approximately 1000 hours. No power losses were detected during the test period. However, one engine experienced camshaft/valve train failure while in service.Engine deposits were measured according to the CRC Diesel Engine Rating system after the test period was completed. Statistical analysis revealed heavier deposits in most areas of the combustion chamber of the three engines fueled with the 50% sunflower oil/50% No. 2 diesel fuel blend. No detrimental engine deposits due to differences in engine size were observed. No injector coking problems or ring sticking problems were encountered. Bearing wear was normal.