Results of comparative examination of the performance characteristics of a compression ignition (CI) engine fuelled with diesel oil and rape methyl esters (RME) have been presented. The engine performance characteristics were assessed from the point of view of energy (effective power and torque of the engine), economy (effective efficiency), and environmental impact (pollutant emission). At the tests, the admixture of summer and winter additives to the rape methyl esters was taken into account. The tests were carried out in the conditions of taking the full-load engine performance vs. engine speed on an AVL Single Cylinder Test Bed provided with a single-cylinder CI research engine AVL 5402, a set of exhaust gas analysers, and instrumentation to control the operation of the whole system. The measurement data were completed and analysed with the use of the AVL PUMA software. In result of the tests carried out, significant differences were found to exist between the engine performance characteristics obtained for the summer and winter versions of vegetable-oil methyl esters. Apart from this, the use of the biofuels under test was found to have a favourable impact on pollutant emission.