The Development of Improved Fuel Specifications for Methanol (M85) and Ethanol (Ed85) 940764

Fuel alcohols, such as M85 (a blend of 85 percent by volume methanol with hydrocarbons) and E_d85 (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 E_d85 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 E_d85 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.

As part of an agreement with the California Energy Commission, General Motors (GM) developed the Chevrolet Lumina Variable Fuel Vehicle (VFV) to operate on any mixture of methanol and gasoline up to M85 (85 percent by volume methanol). Subsequently, due to requests by the states of Wisconsin and Illinois and by the Federal Government, GM developed a version of the Lumina VFV to operate on ethanol-gasoline blends up to 85 percent by volume denatured ethanol (E_d85). (Ethanol is denatured by addition of hydrocarbons at a concentration of about 5 percent by volume.) Currently, GM has sold about 1700 methanol VFVs and about 400 ethanol VFVs. Most of the methanol VFVs are located in California and most of the ethanol VFVs are in the Midwest.

Fuel quality is of prime importance for acceptable performance and durability for VFV customers. Methanol and ethanol fuels are inherently lower in volatility than gasoline fuels and are easily contaminated during manufacture, storage, and distribution. As indicated in the DOE publication, “Fuel Alcohol Formulations” [1], the formulation and purity of methanol and ethanol fuel can affect vapor flammability, cold starting performance, and corrosion.

Results of our studies are presented to illustrate some deficiencies in existing ASTM and California Air Resources Board (CARB) specifications. Based on these studies, we developed GM's specifications for M85 and E_d85.