Exhaust Emissions, Fuel Economy, and Driveability of Vehicles Fueled with Alcohol-Gasoline Blends

Current national interest in alternative fuels has placed considerable emphasis on alcohols, mainly methanol and its blends with gasoline. Vehicle studies with methanol-gasoline and ethanol-gasoline blends showed that adding alcohol to gasoline without carburetor modifications decreased carbon monoxide emissions, volume-based fuel economy, driveability, and performance. Depending on the carburetor's air-fuel ratio characteristics, hydrocarbon and nitrogen oxide emissions and road octane are either increased, decreased, or not affected.

These effects can be explained on the basis of changes in stoichiometry, energy content, combustion temperatures, and detonation resistance caused by the addition of alcohol to gasoline.