During the summer, the U.S. government typically restricts the sale of fuel to a particular blend that evaporates less to mitigate pollution. But the ongoing war in Iran has wreaked havoc on fuel prices all year, so the Environmental Protection Agency and Department of Energy have issued an emergency waiver that allows E10 gas with a higher evaporation rating to be sold starting September 1, two weeks earlier than it normally enters consumer supply.
Throughout much of 2026, the EPA has allowed the sale of gasoline with up to 15% ethanol content, even during the hottest months when it isn’t usually allowed. The rationale is that diluting fuel helps control prices at the pump. But increased ethanol content, as well as higher Reid Vapor Pressure (RVP) values—that’s a measure of evaporation, or volatility—exacerbates ground-level ozone in high temperatures, which poses cardiovascular and respiratory risks for humans. That’s why this stuff is usually relegated to the fall and winter.
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