On May 31, 2019, the U.S. Environmental Protection Agency (EPA) issued a final rule allowing the year-round sale of motor gasoline blends containing up to 15 percent ethanol (E15) and thereby increasing the availability of E15 blends in the United States. Prior to that, E15 was not sold during the summer months, defined as June 1 to September 15, to limit evaporative emissions that contribute to ground-level ozone. Most motor gasoline sold in the United States contains up to 10 percent ethanol (E10). Under free market conditions, some ethanol is added to gasoline for its value as an oxygenate, creating a cleaner burning fuel and raising the octane rating of motor gasoline, which is useful in today’s higher compression, more efficient engines.
