Emission results from a 48-car test evaluation of MMT performance additive

Ethyl Corporation (‘Ethyl’) has conducted extensive fleet testing to investigate the effect of a manganese-based antiknock additive (MMT) on exhaust emissions from production cars. The fleet consisted of 48 cars — six cars each of eight models representing more than 50% of 1988 US sales. Three of each model were tested for 75 000 miles using the base fuel and the other three used the base fuel plus 0.03125 g Mn/gallon as MMT. Results of this testing show that use of the additive will not cause or contribute to the failure of emission control systems. Exhaust back pressure data for the 48-car fleet as well as a test of a close-coupled catalyst at 80 miles/h showed no indication of catalyst distress or plugging. Catalyst conversion efficiency was generally higher for units aged on the MMT fuel. Particulate emission data showed that approximately 12% of the input manganese was exhausted as airborne manganese for the FTP cycle. The significant increase in particulate emissions from addition of MMT reported by the EPA was shown to have resulted from contamination of the fuel with chlorofluorocarbons.