The purpose of the tests described in this publication was to examine the effect of the temperature of the biodiesel burned, resulting from the transesterification of rapeseed oil with methanol, on the level of nitrogen oxides emissions. The tests were carried out on a test stand equipped with a 9.5 kW engine. Electricity was transffered directly to the power grid. The measurements were started after the engine has warmed up, when the oil temperature exceeded 85°C. In the first stage, the engine was loaded with the maximum achievable torque (100%), in the second stage the torque was set at 75% of the maximum value, and for measurements in the third stage the torque was 50% of the maximum value. Three tests were carried out, one for each of the three fuel temperatures: 20, 40 and 55°C.