Influence of ethanol-blended fuels on the emissions from three pre-1985 light-duty passenger vehicles

Tailpipe and evaporative emissions from three pre-1985 passenger motor vehicles operating on an ethanol oxygenated and on a nonoxygenated (base) fuel were characterized. Emission data were collected for vehicles operating over the Federal Test Procedure at 90 degrees F, 75 degrees F, and 40 degrees F to simulate ambient driving conditions. The two fuels tested were a commercial summer-grade regular gasoline (the nonoxygenated base fuel) and an oxygenated fuel containing 8.8% ethanol, more paraffins and olefins, and less aromatics than the base fuel. The Reid vapor pressure (RVP) was adjusted to correspond to that of the base fuel. The emissions measured were total hydrocarbons (THCs), speciated hydrocarbons, speciated aldehydes, carbon monoxide (GO), and oxides of nitrogen (NOx). This study showed a general reduction in tailpipe emissions of THC, CO, benzene, and 1,3-butadiene when tested with the ethanol fuel. The ethanol fuel significantly reduced these emissions from the high emitting vehicle, MU098, at 90 degrees F, 75 degrees F, and 40 degrees F test temperatures. Additionally, the ethanol fuel reduced CO emissions from vehicle BU950, with and without catalyst, and from vehicle CI415 at 40 degrees F. Both formaldehyde and acetaldehyde emissions generally increased when tested with the oxygenated fuel. The acetaldehyde emissions were about double with this fuel. The limited data indicate that most emissions, including toxics, occur during the first 124 seconds of vehicle start-up. Diurnal evaporative emissions were less from the oxygenated fuel, while hot-soak evaporative emissions were greater from the oxygenated fuel (for all vehicles except MU098). Evaporative emissions were generally greatest at the 90 degrees F test temperature.