Unleaded Avgas Transition Faces More Delays And Challenges

To paraphrase Shakespeare, the course of true love — and unleaded avgas — never did run smooth. This was no exception at EAA AirVenture Oshkosh 2026.

Let’s begin at the end. Chris Rocheleau, deputy administrator of the FAA, appeared for the administrator at the “Meet the Administrator” session during the show. He announced that the FAA was indeed publishing the final transition plan for unleaded avgas, as mandated by Congress. Except, the transition plan isn’t final, because the FAA doesn’t know all the answers yet.

Nonetheless, since Congress told the FAA to publish a final transition plan, indeed it has, with the caveat that the final plan is not final and, in fact, it’s not even a plan yet.

Rocheleau went on to say that the industry and the FAA need to approach Congress to explain that despite the mandate, there’s no finality yet.

The next day, he announced he’s leaving the FAA to return to the National Business Aviation Association (NBAA) to serve as its chief operating officer, a move that may have been afoot long before his quixotic announcement at Oshkosh.

In response to his comments, the FAA issued a press release that explicitly stated 2030 is still the deadline. And subsequently, EAGLE (Eliminate Aviation Gasoline Lead Emissions) issued a press release that 2030 is only a goal. No word from the EPA yet on its view.

But during Oshkosh, Rocheleau maintained that there is no one fuel that works for the entire general aviation fleet.

Many in the industry would disagree, including officials with General Aviation Modifications Inc. (GAMI), which received an STC for its G100UL back in 2022, or Swift Fuels, which just received approval to expand its Approved Model List for its 100R unleaded fuel to more than 800 general aviation engine models, though high-performance models are still pending.

ASTM and More

But backing up, there were other startling announcements at Oshkosh about unleaded fuel.

First, GAMI shared — or rather the FAA shared for it — that its G100UL fuel has begun the ASTM specification process. An ASTM task force has been assembled.

Why is this news? Up until now, GAMI officials have said they would not participate in the ASTM process.

At Oshkosh, GAMI’s Chief Engineer George Braly somewhat truculently explained that he intends to support the ASTM application with the reports prepared, and approved, by the FAA on the path to certification of GAMI’s fuel. He observed that if those reports were adequate for the FAA, they should also be adequate for the ASTM task force.

Those will be interesting meetings. We will keep you advised.

GAMI officials underscored that the FAA reauthorization bill directed the administrator to approve the replacement of 100LL with an unleaded candidate when the unleaded fuel is approved for “all or nearly all” aircraft. The FAA’s final transition plan issued at Oshkosh stated that G100UL was approved for use in nearly all aircraft. The replacement approval is still pending, however.

Second, Swift Fuels’ CEO Chris D’Acosta led a fast-paced, revival-spirited meeting, with attestations, statements of faith, and perhaps a few hallelujahs. In the course of that presentation, D’Acosta explained that Swift Fuels had entered into an agreement to have the FAA do the testing of its fuel on the more demanding high-performance engines in the fleet as part of the Piston Engine Aviation Fuels Initiative (PAFI) process.

He held out the prospect that Swift’s fuel might be granted fleetwide approval as that’s the aim of the PAFI process.

What we know about fleetwide approval, though, is a bit concerning.

The FAA has indicated that rather than having an Approved Model List (AML) like an STC, such as GAMI’s G100UL and Swift’s 94UL approvals, the FAA’s fleetwide approval process will instead consist of issuing guidelines and then leaving it up to an A&P/IA to decide whether an aircraft and engine are eligible for operation on the new fuel.

This passes the liability buck from the FAA, which won’t be issuing approvals, to the poor IA who is not typically in a very good position to make such determinations.

And this approach would appear to violate the federal Administrative Procedures Act, which governs how federal agencies create rules, conduct hearings, and make decisions.

And, finally, that decision by the FAA is likely to raise legal challenges.

This may, of course, not be the final form of the approval, but even as a concept it’s somewhat concerning.

Several commenters questioned why Swift Fuels was approaching approval in an apparently upside-down fashion. Why not test the most difficult combustion chamber operating conditions first? And then, if necessary, back away to less challenging applications.

There are some apparent reasons that Swift’s bottom-up approval approach, approving the least demanding engines first, may work well economically. Swift is already selling 94UL at up to 60 airports and, in the next couple of months, those 94UL pumps will begin pumping Swift’s 100R. That’s possible because Swift has prioritized getting 100R approval for the current Approved Model List (AML) roster of lower compression engines that can use 94UL.

That gives Swift an earlier distribution of unleaded 100-rated fuel, which will give it an advantage.

If there are lessons to be learned in the field — and industry experience is that there are always lessons learned in the field — the earlier Swift gets its fuel on the market, the more time it will have to address any issues that may emerge.

Will Mods Be Needed?

Those who were able to speed-read the charts Swift presented noted that even the most optimistic case showed only 95% of the fleet would be approved. That leaves more than 10,000 airplanes on the ground. Other analysts have suggested it’s closer to 25,000 aircraft on the ground.

Those airplanes might be able to fly on Swift’s fuel after some modifications, but as yet, we don’t know what modifications might be necessary. Swift officials say it may be just retarding the timing a few degrees (which in many cases would require an STC).

No one has as yet committed to providing the resources for gaining the necessary FAA approvals for any such mods, and indeed, some aircraft may not meet certification standards afterwards.

The devil is in the as yet missing details.

The Third Candidate

What about the third unleaded fuel candidate from LyondellBasell and VP Racing, which is the only fuel remaining in the PAFI program?

While the Lyondell/VP Racing consortium has almost always been represented by Lyondell research engineer Dan Pourreau, he was not in evidence at Oshkosh this year. Instead, the update message was delivered by VP Racing’s Mark Walls, Director of R&D, who extolled VP Racing’s expertise in blending a variety of specialty gasolines. But this didn’t lend itself as much as previous sessions to a technical discussion of the fuel’s certification effort.

LyondellBasell and VP Racing and PAFI officials are now targeting late 2027 approval for the new 100E fuel.

One thing we do know is that Lyondell officials have said using the company’s new fuel in the 5% of aircraft that can’t use unleaded fuel right now might require different pistons or cylinders to operate at a lower compression ratio.

Certification and compliance with such a change would be lengthy and costly.

Market Forces at Work?

Finally, on opening day of AirVenture, a presentation by the FAA and EAGLE was held. EAGLE, a government-industry initiative, has the express mission of transitioning general aviation to unleaded fuel by 2030.

After the presentation, the FAA’s Paul Wrzesinski and the Aircraft Owners and Pilots Association’s Acting Co-President Katie Pribyl entered into a confounding conversation in response to a question as to whether the unleaded transition would be market driven. They both said yes, it would be market driven.

The questioner added to his query: “How do we cope with the fact that the candidate fuels are not mutually compatible?”

The answer to that was quite muddled. Wrzesinski responded that we need one fuel. Well, if we’re to be market driven, how do we get to one fuel? By FAA regulation. Then just how is this market driven with only one fuel? The ensuing word salad shed no light on the answer.

The course of true love and unleaded avgas continues to not run smooth.

So Is Lead Really Going Away?

In my first story for General Aviation News, “Why The 2030 Deadline For Unleaded Avgas Is Final,” I noted that the single remaining TEL manufacturer in the west, Innospec, had announced it plans to stop making TEL in the 2028-2029 time frame, with inventory available to support leaded avgas blending until the sunset date of 2030.

Since the message at Oshkosh was that the 2030 deadline would have to be pushed, officials with EAGLE, Swift Fuels, and others maintained that my article was in error and that Innospec would continue to manufacture TEL as long as we need it.

Swift Fuels’ D’Acosta quoted Innospec to the effect that there was no shutdown timeline to share. Those of us practiced in corporate public relations releases will recognize the vast difference between “there is no timeline to share” and our earlier reporting that the TEL plant shutdown is likely planned by the end of this decade.

However, a few weeks after Oshkosh, Innospec did release an “information update” saying that “no firm timelines on the cessation of TEL-B production have been made.”

The update added that the company “fully supports the EAGLE initiative and the industry goal to eliminate leaded aviation fuels in piston-engine aircraft safely by the end of 2030.”

“Crucially, we fully recognize our responsibility to the GA industry as the last manufacturer of tetraethyl lead in the world and the key role we will have in ensuring that 100 low-lead fuel is available during any transition to unleaded fuel,” it noted.

Innospec’s TEL manufacturing capacity hugely exceeds the TEL demand for avgas. If the industry can ever establish a credible timeline for lead phaseout, Innospec should be able to stockpile adequate TEL to meet demand through that date.

Another Solution?

A master’s thesis candidate from the University of North Dakota made two presentations during the show on his solution for 100LL: Keep making it.

Patrick Ealy asserts that the EPA’s avgas lead contribution numbers are wrong, by an order of magnitude. Avgas lead isn’t 50% of U.S. lead emissions, but rather less than 5%, according to the studies he cited.

Moreover, he posits creating a lead capture mechanism for general aviation aircraft that use 100LL: An anode with an electric power supply installed in every aircraft’s exhaust system. Then at oil change, the two-pound lead-covered anode would be removed for recycling and replaced with a fresh one.

It wasn’t clear, absent lead police at the end of the runway, how or why pilots and aircraft owners might indulge this system.

Ealy was quite frank that he’s not an engineer, and that the electric anode is just a concept, not something that has been designed or evaluated for feasibility. Indeed, devices that increase exhaust system back pressure both reduce power output and increase the likelihood of detonation.

Still, it makes for an interesting thought model.

Ealy’s facts were not carefully checked, but it’s early days for his thesis.

For instance, he also suggested that we could reduce aircraft lead emissions just by adopting VLL, very low lead avgas.

But already, six of the seven U.S. refineries have effectively done that, so no more reductions are available.

The one refinery that hasn’t adopted VLL, where I used to serve as the process planning manager, is incapable of achieving 100LL specification without the lead, due to an intricate collision of feedstocks and process configuration.

Fixing that problem would cost over $30 million in 2010 dollars. That’s not an attractive investment for the sunsetting, very small, leaded avgas business.