Why It Matters

A decades-old regulatory quirk is forcing Congress and the White House into an uncomfortable alliance and a fight with the oil refining industry over whether a corn-derived fuel blend can be sold at gas stations year-round. A Congressional Research Service report updated June 5 describes how E15 fuel, a blend of up to 15 percent ethanol and 85 percent gasoline, is effectively banned from summer sale under the Clean Air Act's volatility rules, even though federal scientists concluded more than a decade ago there is "no technical reason" to treat it differently from the E10 blend that fills most American gas tanks today.

The Big Picture

The Science Behind Summer Restrictions

The Clean Air Act caps gasoline volatility during the high-ozone summer months of June 1 through September 15 at 9.0 pounds per square inch of Reid Vapor Pressure, a measure of how readily fuel evaporates in heat. Evaporation releases volatile organic compounds that contribute to ground-level ozone and smog. The law gives E10, the standard 10 percent ethanol blend, a one-pound waiver, allowing it to be sold at up to 10.0 psi, but E15 gets no such exemption, effectively locking it out of the summer market under normal circumstances.

The wrinkle is that the science doesn't clearly support that distinction. The National Renewable Energy Laboratory (now the National Laboratory of the Rockies) reported in 2012 that the vapor pressure impact of 15 percent ethanol "is indistinguishable from that of 10 percent ethanol in gasoline for all volatility seasons and base hydrocarbon vapor pressures." In other words, the regulatory barrier to E15 ethanol fuel year-round sale appears to rest on statute, not on a meaningful difference in air quality risk.

The Waiver Workaround

The Clean Air Act does allow EPA to issue temporary fuel waivers lasting up to 20 calendar days when extreme and unusual fuel supply circumstances exist. Achieving year-round E15 availability through this mechanism requires issuing a consecutive series of rolling waivers, a legally cumbersome approach that creates ongoing regulatory uncertainty for fuel retailers and blenders.

On March 25, EPA issued the first nationwide fuel waiver for the 2026 summer driving season, citing "ongoing issues in the Middle East, among other events" as justification. EPA also stated its intention to keep issuing renewals "until such time as the circumstances described in this action are no longer present," signaling the agency plans to sustain E15 access through the summer under the emergency authority framework.

Congress Moves on Legislation

The House passed H.R. 1346 in May, a measure which would permanently allow E15 to be sold year-round and would also make changes to the small refinery exemption component of the Renewable Fuel Standard. In the Senate, S. 593 would similarly allow year-round E15 sales. This is not the first attempt. E15 legislation was included in a short-term spending bill introduced in the House in December 2024 but was stripped out of the final continuing resolution that became law.

The CRS report also flags unresolved questions Congress will need to answer. For example, who pays to install E15-compatible fueling infrastructure; whether broader E15 use would raise environmental concerns; what effect year-round sales would have on the Renewable Fuel Standard (RFS) program; and whether California's October 2025 decision to authorize E15 sales will reshape national ethanol and fuel markets while state entities review whether it meets California's clean air requirements.

Political Stakes

For the Administration

President Trump signed Executive Order 14156, "Declaring a National Energy Emergency," on January 20, 2025, which directed the EPA Administrator to consider issuing emergency fuel waivers to allow year-round E15 availability to address projected gasoline supply shortfalls. The order directed consideration of waivers, but it did not mandate them, preserving EPA's statutory discretion. EPA's nationwide waiver in March shows the administration operationalizing that directive.

Corn farmers and ethanol producers in Iowa, Illinois, Nebraska, and other agricultural states are core constituencies for the Republican coalition, and year-round E15 access is a long-standing priority for that bloc. The administration is simultaneously pursuing the executive waiver path for immediate effect, and backing the legislative track for a permanent fix.

For the GOP

Some members of Congress have stated that "any legislative movement on E15 must be conditioned upon meaningful reforms to the Renewable Fuel Standard." H.R. 1346's changes to the small refinery exemption, a provision that shields smaller petroleum refiners from RFS compliance obligations, puts the oil refining industry and the ethanol industry on opposite sides of the same bill. Navigating that tension in the Senate, where the bill has not yet passed, is the next test.

For Democrats

The report does not frame the E15 debate as a partisan issue, and the CRS analysis is agnostic on whether year-round E15 sales are net positive or negative for consumers. The questions are genuinely open on whether E15 would reduce gasoline prices, whether it raises new environmental concerns, and whether the rural economy would benefit.

The Bottom Line

The Trump administration has used emergency EPA waivers to keep E15 on the market through the summer of 2026, and the House has passed legislation to make that access permanent. But the waiver mechanism is legally limited and geopolitically contingent. It depends on EPA continuing to certify that unusual fuel supply circumstances exist. A permanent statutory fix requires Senate action, and that path runs directly through a fight over Renewable Fuel Standard reforms that pits corn-state Republicans against refining-state Republicans. Until that is resolved, year-round sale of E15 fuel remains a policy goal held together by a series of rolling 20-day emergency orders.

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