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 %), T50 (195, 215, and 235 degrees F), and T90 (295, 330, and 355 degrees F). There were statistically significant interactions between ethanol and T90 for NMHC, ethanol, and T50 for CO and ethanol and T50 for NO(x). NMHC emissions increased with increasing ethanol content at the midpoint and high level of T90 but were unaffected at the low T90 level. CO emissions decreased as the ethanol content increased from the low to the midpoint level for all levels of T50, but between the 5.7 and 10% ethanol levels, CO showed only an increase for the high level of T50. NO(x) 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 T90 level, with NMOG, acetaldehyde, benzene, and 1-,3-butadiene all found to increase with increasing ethanol content.