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Fuel alcohols, such as M85 (a blend of 85 percent by volume methanol with hydrocarbons) and Ed85 (a blend of 85 percent by volume denatured ethanol with hydrocarbons), are inherently involatile at low temperatures and may contain soluble or insoluble contaminants. We explored the adequacy of existing specifications for M85 and Ed85 by studying fuel effects on cold starting and vapor flammability, and fuel contaminant effects on materials compatibility and filter plugging. These studies demonstrated deficiencies in existing specifications. Therefore, we developed General Motors specifications for M85 and Ed85 to improve vehicle performance and durability. Key features include a Cold Starting Performance Index to improve wintertime starting, a conductivity and chloride ion specification to reduce corrosion, and a particulate contamination limit to reduce filter plugging.

The emissions and performance of five diesel fuels, covering a range of cetane numbers and volatilities, were evaluated at three speeds and equivalence ratios in a single-cylinder, DI diesel engine. Graphical comparisons and regression analysis of the data revealed that cetane number and to a lesser extent volatility are the fuel parameters that most strongly influence emissions and performance, with higher cetane number and higher volatility fuels providing the best performance and lowest emissions. Trends toward lower cetane number, lower volatility fuels must be reversed to meet the emissions and performance standards of future light-duty DI diesel engines, should such engines be developed for use in automotive applications.