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In 2008-2009, EPA and DOE tested fifteen 2008 model year Tier 2 vehicles on 27 fuels. The fuels were match-blended to specific fuel parameter targets. The fuel parameter targets were pre-selected to represent the range of fuel properties from fuel survey data from the Alliance of Automobile Manufacturers for 2006. EPA's analysis of the EPAct data showed that higher aromatics, ethanol, and T90 increase particulate matter (PM) emissions. EPA focused their analysis only on the targeted fuel properties and their impacts on emissions, namely RVP, T50, T90, aromatics, and ethanol. However, in the process of fuel blending, at least one non-targeted fuel property, the T70 distillation parameter, significantly exceeded 2006 Alliance survey parameters for two of the E10 test fuels. These two test fuels had very high PM emissions. In this study, we examine the impacts of adding T70 as an explanatory variable to the analysis of fuel effects on PM.

Laboratory bench tests were conducted to simulate both the diurnal and the hot-soak (carburetor only) parts of an evaporative emissions test with gasolines containing various alcohols and ethers. The mass of vapor generated during each test and the detailed composition of the vapor were determined for each fuel. Using published atmospheric reactivity scales, the ozone-forming potential of the vapor was estimated. Based on the scale of maximum incremental reactivities, which the California Air Resources Board has proposed for future emissions standards, the diurnal test results showed that the addition of methyl tertiary-butyl ether (MTBE) or ethyl tertiary-butyl ether (ETBE) to gasoline resulted in about the same or lower total vapor reactivity compared to the gasoline alone.