A Detroit Diesel 6V92TA MUI engine was operated on several blends of EPA #2 diesel, California ARB #2 diesel, soya methyl ester (SME) and canola methyl ester (CME). Various fuels and fuel blend characteristics were determined and engine emissions from these fuels and blends were compared. Increasing percentages of SME and CME blended with either ARB or EPA diesels led to increased emissions of NOx, CO2 and soluble particulate matter. Also noted were reductions in total hydrocarbons, CO and insoluble particulate matter. Chassis dynamometer tests conducted on a 20/80 SME/ARB blend showed similar emissions trends. The data suggest that certain methyl ester/#2 diesel blends in conjunction with technologies that reduce the soluble fraction of particulate emissions merit further exploration as emissions reducing fuel options for North American mass transit sectors (excepting California, which mandates ARB diesel).