This research presents the differences between the exhaust emission parameters when biodiesel and biodiesel blends are used instead of Ultra-Low Sulfur Diesel (ULSD). Measurements have been conducted on three commercial light-duty engines. The engines include an Audi 1.9 TDI that lives up to the requirements of Euro 2, a Peugeot 1.6-liter common rail with original oxidation catalyst and EGR that lives up to the requirements of Euro 4 and a Peugeot 1.6-liter common rail with original Diesel Particulate Filter (DPF) and Exhaust Gas Recirculation (EGR) that lives up to the requirements of Euro 4.Tests were performed on a dynamometer running steady state in five representative modes drawn from the ISO 8178 test procedure.The reference diesel was in accordance with EN 590. The biodiesel blends are based on a new EN 14214 animal fatty acid methyl ester (AFME). Biodiesel blends consisting of 20% biodiesel and 100% biodiesel have been chosen for the different gaseous emission measurements where NO, NO₂, CO, CO₂ and HC are measured. Also polycyclic aromatic hydrocarbons (PAH) were measured in the 50% load mode. In order to get an insight into the nano particle emissions from the Euro 4 and Euro 2 engines, the particle number concentration and the particle size distribution were characterized.The results showed that the levels of some emission parameters differed when biodiesel was compared with ULSD. Differences in the emission parameters were also found when the three engine types were compared. Especially the NO₂ emission showed a significant difference with regard to engine types and fuels.