Results of an examination of the combustion process in a compression ignition (CI) engine fuelled with diesel oil and rape methyl esters (RME) with admixtures of summer and winter additives have been presented. The examination was undertaken to assess whether rape ethyl esters may be legitimately recognized, from the point of view of the properties of the combustion process, as substitute fuels for diesel oil. The tests were carried out in the conditions of taking the full-load engine performance vs. speed curve on an AVL Single Cylinder Test Bed provided with a single-cylinder CI research engine AVL 5402. The full-load torque and effective efficiency curves were taken and the maximum values of the indicated pressure and the corresponding crank angle values were determined. The extreme values of the derivative of the indicated pressure with respect to the crank angle were established as well. To plot the curves that would visualize variations in the quantities characterizing the combustion process, the CONCERTO data processing platform was used. The maximum values of the air-fuel mixture temperature were measured, with finding out the corresponding crank angle values. The characteristics determined for diesel oil and rape methyl esters with an admixture of summer additives were found to be very similar to each other, while for the winter biofuel version, the characteristics were markedly different.