The effects of using neat and blended (30% vol.) biodiesel, obtained from Rapeseed Methyl Ester (RME) and Jatropha Methyl Ester (JME), in a Euro 5 small displacement passenger car diesel engine have been evaluated in this paper.The impact of biodiesel usage on engine performance at full load was analyzed for a specifically adjusted ECU calibration: the same torque levels measured under diesel operation could be obtained, with lower smoke levels, thus highlighting the potential for maintaining the same level of performance while achieving substantial emissions benefits.In addition, the effects of biodiesel blends on brake-specific fuel consumption and on engine-out exhaust emissions (CO₂, CO, HC, NOx and smoke) were also evaluated at 6 different part load operating conditions, representative of the New European Driving Cycle. Emissions were also measured at the DPF outlet, thus providing information about after-treatment devices efficiencies with biodiesel. The application of a specifically adjusted engine calibration showed a rise of fuel consumption, due to the lower energy content of biodiesel, at same fuel conversion efficiency and comparable CO₂ emissions. An appreciable increase of CO and HC emissions at low load could be noticed, along with a considerable smoke emission reduction.Finally, soot-NOx trade-off were also analyzed for three different engine operating points, in order to gather detailed information about further possible emissions benefits that could be achieved through a more extensive ECU recalibration.