An experimental program was conducted by the Energy Research & Development Administration's Bartlesville (Okla.) Energy Research Center to determine the effect on exhaust emissions and fuel economy when methanol is added to conventional motor fuel, that is, gasoline. Ten 1974 and 1975 model vehicles were used in the study. Ambient temperature was varied from 20° to 100°F to determine temperature effects while using methanol/gasoline blends. Emissions were generally modified as a consequence of the fact that the addition of methanol to gasoline alters both the fuel vapor pressure and the stoichiometry of the air-fuel mixture. Fuel economy was generally decreased by methanol addition.Moderate mileage accumulation using 10% methanol fuel showed no deterioration either in emissions control or of fuel-related engine components. Driveability differences between methanol 10% blends and gasoline were detectable but were judged not to be objectionable.