Emissions of heavy duty engines using hydrocarbon fuels and rape seed methyl ester (RME) were measured according to the ECE R49 test procedure. The effect of fuel density on engine power was taken into account in the ECE R49 tests. The two reformulated fuels tested had sulphur below 50 ppm, aromatics below 20 vol-%, cetane number over 49 and reduced triaromatic content.Particulates were measured in a AVL Mini Dilution Tunnel 474 and gaseous unregulated hydrocarbons by Siemens FTIR.Reformulation reduced NOx by 5 to 12 %, particulates by 10 to 25 % and Ames mutagenicity by 56 to 74 %. RME increased NOx by 4 to 9 %, reduced particulates by 0 to 33 % and the mutagenicity by 17 %.Cetane number was found to be not important in reducing emissions. Low fuel triaromatic and low particulate PAH content reduced the mutagenicity of particulates.