This paper demonstrates the results of testing the performance of tractors using fossil diesel, biodiesel, and blends of biodiesel and fossil diesel. The results of tests conducted in stationary and non-stationary conditions indicate that, in contrast to fossil diesel, the use of biodiesel and blends of biodiesel and fossil diesel reduce the power of engine and drawbar power, and increase specific fuel consumption. Thermal efficiency slightly improves with biodiesel blends. The differences become notable with bigger share of biodiesel in the blend. However, the changes are less notable regarding the differences in heating value, which is the result of complete combustion. Use of different fuels, compared to use of fossil diesel only, reduces the CO emission and temperature of exhaust fumes, and increases the CO2 emission and NOx. At maximum load, the difference between the parameters measured in stationary and non-stationary conditions is minimal. On the other hand, at lower loads, the load variable formed in non-stationary conditions of testing becomes noticeable which results in greater differences. However, decrease in engine power and increase in fuel consumption using biodiesel significantly deteriorated the exploitation characteristics of plowing tractors (production efficiency was reduced by 12.87% and fuel consumption per unit of cultivated area was increased by up to 21.63%). (C) 2018 Elsevier Ltd. All rights reserved.