Effects of Methanol and Fuel Sulfur Concentration on Tailpipe Emissions in a Production Variable Fuel Vehicle

Conventional and speciated tailpipe emissions from a 1992 Chevrolet VFV Lumina were measured to: 1) document differences between M85 and M0; 2) determine whether differences between M85 and M0 were due to the lower sulfur content of M85. The test fuels were M0-A (industry average gasoline), M85-A (a splash blend of 85% methanol and 15% M0-A), and M85-S, which was M85-A doped with thiophene to increase its sulfur concentration to a level equivalent to M0-A. Changing fuel from M0-A to M85-A decreased CO, benzene, 1,3-butadiene, and hydrocarbon-equivalent organic emissions (OMHCE), and reduced both specific reactivity and ozone forming potential of the exhaust. However, methanol and formaldehyde emissions increased. These results are consistent with those of a prototype fleet studied in the Auto/Oil Air Quality Improvement Research Program. Results with M85-S indicate that the inherently lower sulfur concentration of M85-A compared to M0-A did not significantly affect differences in total organic emissions or their ozone forming potential; however fuel sulfur concentration did have a significant impact on CO and benzene emissions differences between M85-A and M0-A. Lower carbon consumption with M85 compared to M0 likely contributes to reduced OMHCE and CO emissions.