Effects of fuel ethanol content and volatility on regulated and unregulated exhaust emissions for the latest technology gasoline vehicles

Oxygenate content and fuel volatility (distillation) variables are important parameters affecting vehicle exhaust emissions, and data on their effects on the latest technology vehicles are quite limited. For this study, 12 California-certified LEV to SULEV vehicles were tested on a matrix of 12 fuels with varying levels of ethanol concentration (0, 5.7, and 10 vol %), T-50 (195, 215, and 235 degrees F), and T-90 (295, 330, and 355 degrees F). There were statistically significant interactions between ethanol and T-90 for NMHC, ethanol, and T-50 for CO and ethanol and T-50 for NOx. NMHC emissions increased with increasing ethanol content at the midpoint and high level of T-90 but were unaffected at the low T-90 level. CO emissions decreased as the ethanol content increased from the low to the midpoint level for all levels of T-50, but between the 5.7 and 10% ethanol levels, CO showed only an increase for the high level of T-50. NOx emissions increased with ethanol content for some conditions. Non-methane organic gases (NMOG) and toxic emissions were examined for only a subset of fuels with the highest T-90 level, with NMOG, acetaldehyde, benzene, and 1-,3-butadiene all found to increase with increasing ethanol content.