Although the substitution of rapeseed-oil methylesters for conventional diesel fuel is already a commercial practice in many countries of central Europe, the use of biodiesel has not yet been developed in Greece and other Southern Europe countries because of the lack of sufficient rapeseed cultivation. However, vegetable oils of other types, such as sunflower oil and corn oil, are abundant in many Mediterranean areas, and they seem to be attractive candidates for biodiesel applications. In this paper the results of small fleet tests are presented, in which vehicles were fuelled with blends of mineral diesel fuel and sunflower and corn oil biodiesel. It was observed that biodiesel resulted in reduced black-smoke opacity, and no significant increase of engine wear was observed. The drivers were enthusiastic and reported that they noticed no change in vehicle performance.