[5] In the United States, the Environmental Protection Agency (EPA) had authority to mandate that minimum proportions of oxygenates be added to automotive gasoline on regional and seasonal basis from 1992 until 2006 in an attempt to reduce air pollution, in particular ground-level ozone and smog.
As of 2023, the EPA continues to require the use of oxygenated gasoline in certain areas during winter to regulate carbon monoxide emissions; however, the programs to fulfill its conditions are implemented by the states.
In addition to this North American automakers from 2006 onwards promoted a blend of 85% ethanol and 15% gasoline, marketed as E85, and their flex-fuel vehicles, e.g. GM's Live Green, Go Yellow campaign.
US Corporate Average Fuel Economy (CAFE) standards give an artificial 54% fuel efficiency bonus to vehicles capable of running on 85% alcohol blends over vehicles not adapted to run on 85% alcohol blends.
Methyl tert-butyl ether (MTBE) was the most common fuel additive in the United States, prior to government mandated use of ethanol.