Unleaded fuel takes center stage at AirVenture

During a “Meet the Administrator” forum on July 23, FAA Deputy Administrator Chris Rocheleau touched on a wide range of topics affecting general aviation and suggested the “aggressive” unleaded fuel transition timeline may slip beyond the current 2030 goal.

“One of the things I've certainly learned in prior roles, but certainly in this role as deputy administrator, is as soon as you set that date... someone's going to change it for you, one way or the other,” said Rocheleau. “And I can tell you with confidence, we're not going to set an arbitrary date... without making sure that whatever we're going to put in those aircraft [is safe].”

EAGLE forum

Rocheleau’s comments followed a July 20 forum hosted by the Eliminate Aviation Gasoline Lead Emissions (EAGLE) initiative, which is a joint government-industry partnership that includes AOPA and other key stakeholders.

Paul Wrzesinski, the FAA senior technical specialist for aviation fuels, outlined parts of the agency's unleaded fuel transition plan, which will be published in the coming weeks—and pointed to changes between it and the previously published draft plan from early 2026.

“We wanted to utilize [public comments] to strengthen the transition plan, to see where we needed to fill in details and gaps or where things were unclear,” said Wrzesinski.

Wrzesinski said those comments influenced changes to the transition plan, including ongoing communication.

“We really want to recommit to being able to engage and be able to distribute information as we go through these fuel evaluations and authorizations,” he said.

As a result, the FAA plans to release new versions of the transition plan after each phase. The agency also plans to publish two additional documents soon: an FAQ on unleaded fuel and a summary of the input received during the public comment period in early 2026.

The plan calls for the transition to occur in four phases. The first phase includes authorizing fuels and doing comparison testing. The second focuses on unleaded fuels gaining market experience—providing valuable insights for fuel producers, aircraft owners, fuel retailers, and others.

The third and fourth phases focus on the wide-scale transition—first in the Lower 48, with a goal of completing the work by 2030, followed by Alaska two years later.

At the same time, AOPA acting Co-President Katie Pribyl highlighted the need for one high-octane unleaded fuel and said that the goal of transitioning by 2030 may not happen.

“The transition plan assumes right now that the market is going to decide, and that's probably not realistic,” said Pribyl. “We want the FAA to have a role in that beyond just approving fuels. They're doing the testing. We believe that they're in the best position to help the industry come to that decision on what that fuel is going to be.”

“There's a lot of really important testing that we have in front of us, especially around materials compatibility and the commingling testing,” added Pribyl. “So that's really important information and data that's going to inform this process and will inform whether or not we can hit that 2030 goal.”

Fuel provider updates

Each developer also held forums on their respective fuels, presenting technical updates, testing milestones, and discussion of opposing philosophies on how to best replace 100LL.

It’s also worth noting that each developer is pursuing a different combination of pathways toward both FAA approval and industry acceptance through ASTM International.

Swift Fuels (100R)

Swift Fuels CEO Chris D’Acosta took the stage shortly after EAGLE’s forum concluded, where he discussed recent 100R progress.

Days prior to AirVenture, on July 14, Swift announced that FAA has issued an amended approved model list (AML) for a supplemental type certificate (STC) that now allows the use of 100R in more than 1,600 aircraft models and 1,200 engine models, which Swift says account for about 55 percent of current 100LL fuel consumption.

The next day, Swift announced it joined the Piston Aviation Fuels Initiative (PAFI), the program created to support fleet authorization of unleaded fuel.

D’Acosta discussed components of 100R including ethyl tert-butyl ether (ETBE), which boosts octane and also enables cleaner combustion, and “AV-ADD,” a proprietary additive that “allows the fuel to resist valve-seat recession, to resist intake coking, to keep the engine clean, and operate effectively.”

Swift highlighted a 407-hour high-stress endurance run on a Lycoming engine at Purdue University. A subsequent teardown revealed immaculate parts, no ring sticking, no excess carbon, and parts within normal limits.

As production and distribution of 100R begins, Swift plans to cease production of UL94, which was first introduced in 2015. But D’Acosta pointed to UL94’s existing distribution network—with sales in 29 states and 34 countries—and said that Swift will begin 100R sales “soon.” Swift also offers a “forever STC,” which will provide a free 100R STC upgrade to existing UL94 STC holders.

VP Racing/LyondellBasell (UL100E)

At its July 22 seminar, VP Racing, which is developing UL100E with LyondellBasell, said more than 80 percent of the existing GA fleet will need no engine modifications to use its fuel.

Mark Walls, VP Racing’s director of research and development, said that some high-performance or turbocharged engines will need minor timing adjustments to maintain safety margins, but that those changes will not affect engine performance or fuel economy.

“You're going to hear, ‘Yes, you're going to have to pull some timing out of this engine or that engine,’ and the main concern is, ‘Oh, we're going to lose a lot of power or we're going to lose fuel economy.’ The data's not showing that. The data's showing that there's really no negative effects on power and fuel economy across these engines,” said Walls.

Walls also described compatibility testing that is underway through PAFI. He says there have been no issues with materials compatibility—testing that included at least 229 materials in 14 categories (including bladders, seals, hoses, paints, and primers)—as well as paint tests, wing circulation, and ensuring UL100E won’t cause older fuel bladders to leak.

Walls also addressed cost, as VP Racing expects the price of UL100E to closely mirror 100LL.

“Our fuel is made of common components. They're not specialty components that only one company in the world might maybe make it sometimes,” said Walls. “These are easy-to-get components anywhere in the world, so we can have the ability to make it across the U.S., across the Americas, and across Europe.”

Walls said that UL100E, which earned a test specification from ASTM in 2025—the first step toward earning industry approval—will be put up for a vote on a production specification—the industry’s final stamp of approval—in the coming weeks. Meanwhile, LyondellBasell and VP Racing are seeking fleet authorization—as opposed to STCs—which the FAA expects to complete in 2027.

GAMI (G100UL)

At General Aviation Modifications Inc.’s forum on July 23, cofounder and Chief Engineer George Braly said that G100UL is the only high-octane “drop-in” replacement for 100LL that has FAA STC approval for every spark-ignition piston airplane and engine—and that fuels requiring timing adjustments or power degradation do not qualify as “drop-in” replacements.

Braly addressed what he called an “incredible amount of fear, uncertainty, and doubt,” about G100UL, which centers around materials compatibility concerns—specifically around rubber O-ring swelling, fuel tank sealant degradation, and paint damage.

Braly contended that reports of leaks trace back to airplanes with 20- to 50-year-old fuel tanks and old nitrile seals that degrade over the same timeframe with 100LL. Braly pointed to firsthand experience after GAMI noticed leaking and staining around the sump of its Cirrus SR22, which has been flown on G100UL since 2010.

“We changed the O-ring for a Viton O-ring and polished it off in a few minutes, and it looks pristine,” said Braly. “Use of modern materials for the O-rings and gaskets will largely mitigate a lot of these risks.”

He also said Flame Master, a major sealant manufacturer, tested its full line of polysulfide and polythioether sealants with G100UL and reported 100-percent passing results.

As for paint damage, Braly said the issue lies with aging aircraft, not the use of G100UL.

G100UL is currently the only commercially available high-octane unleaded fuel and is sold at four airports in California, Texas, and Mississippi.

GAMI also recently engaged with ASTM to seek a production specification for G100UL to earn industry acceptance of its fuel.

Tetraethyllead (TEL) supply concerns

The AirVenture forums were held in the midst of significant concern about the continued availability of tetraethyllead (TEL), the lead additive used in 100LL aviation gasoline. Innospec is the sole provider of TEL to the United States and is based in the United Kingdom.

Innospec says there is no date scheduled for ceasing production of TEL, and the company has committed to working with industry stakeholders.

The work ahead

Swift, VP Racing, and GAMI all say their fuels can be safely mixed with 100LL. The FAA is testing the ability to mix each fuel with 100LL as part of the transition plan, as well as the ability to mix a combination of unleaded fuels.

“A lot of work has gone into developing these three unleaded fuels,” said AOPA Senior Vice President of Government Affairs and Advocacy Jim Coon. “We still have a ways to go and we need to fully understand, through data, the impact each fuel could have on airframes and aircraft performance and find a way forward that is safe and best suits the needs of pilots and aircraft owners.”