Fuel economy and emissions of light-duty vehicles fueled with ethanol-gasoline blends in a Mexican City

The government of Mexico is mandating increased use of gasoline-ethanol blends as a method for reducing air pollution. However, tests on light-duty vehicles have revealed mixed results in terms of fuel economy and emissions. In addition, little information on the performance of light-duty vehicles fueled by gasoline-ethanol blends exists outside the conditions in Mexico City. Fuel economy and emission factors for commercial Regular (87 octane) and Premium (92 octane) gasoline were compared to corresponding 5% v/v (E05R/E05P) and 15% v/v (E15R/E15P) ethanol blends under the conditions in Monterrey, Mexico, the third largest urban center in the country. Fuel economy was estimated under real-world driving conditions. CO2, CO, NOx, and unburned hydrocarbons (HC) emissions were measured for cold- and hot-start tests, as well as for constant-speed (40 km/h) real in-city driving. The highest fuel economy was achieved with pure gasoline, which decreased by as much as 4.4% when an E05R gasoline blend was used and as much as 9.9% when an E15R blend was evaluated. For the Premium blends, the fuel economy decrease was lower: 2.9% and 5.5%, respectively. Even more significantly, the newest vehicles tested experienced the lowest decrease in fuel economy. Overall, the Premium blends, and in particular the E15P blend, resulted in decreased CO, NOx, and HC emissions. However, mixed results for NOx emissions were obtained during the start tests. In addition, HC emissions were higher for the Premium blends compared to the corresponding Regular blends. CO2 emissions changes were not significant for the constant-speed tests.