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Due to continuing reductions in EPA's emission standard values for exhaust particulate emissions, industry production has shifted towards engines that produce very low amounts of particulate emissions. Thus, it is very possible that future engines will challenge the error range of the current instrumentation and procedures used to measure particulate emissions by being designed to produce extremely low levels of particulates. When low particulate emitting engines are sampled at low flowrates, the resulting filter loadings may violate the minimum filter loading recommendation in the Heavy Duty Federal Test Procedure [1]. Conversely, higher flow rates may be an inappropriate option for increasing filter loading due to the possibility of stripping volatile organic compounds from the particulate sample or otherwise artificially reducing the accumulated mass [2].

Six in-use vehicles were tested on a baseline gasoline and nine gasoline/ethanol blends to determine the effect of ethanol content in fuels on automotive exhaust emissions and fuel economy. The baseline gasoline was representative of average summer gasoline and served as the base from which the other fuels were blended. For the majority of the vehicles, total hydrocarbon, and carbon monoxide exhaust emissions as well as fuel economy decreased while NOx and acetaldehyde exhaust emissions increased as the ethanol content in the test fuel increased. Formaldehyde and carbon dioxide emissions were relatively unaffected by the addition of ethanol. The emission responses to the increased fuel oxygen levels were consistent with what would be expected from leaning-out the air/fuel ratio for a spark ignition engine. The results are shown graphically and a linear regression is performed utilizing the method of least squares to investigate statistically significant trends in the data.

An analysis of the potential Reid Vapor Pressure (RVP) impacts of the commingling of ethanol fuels with non-ethanol fuels has been done. This analysis includes a computer model that tracks such variables as owner brand loyalty, fill-up patterns, ethanol fuel market share and percent ethanol in the fuel tank to determine the RVP boost that is associated with the use of ethanol as a gasoline oxygenate as it intermingles with non-ethanol fuels in vehicle fuel tanks. Results indicate that the use of ethanol oxygenated fuels can cause, in some cases, a significant increase in gasoline RVP, thus leading to higher evaporative emissions.