A fleet wide approval for an unleaded fuel for general aviation is expected in the third quarter of 2025.
That’s the key takeaway from an April 2024 update from representatives of Eliminate Aviation Gasoline Lead Emissions (EAGLE), an industry-government initiative launched in 2022.
The one remaining fuel in the government’s testing program, known as the Piston Aviation Fuels Initiative (PAFI), is UL100E from LyondellBasell/VP Racing.
It is the only fuel to get through the first three phases of testing and is now in what the FAA calls “full-scale” testing, which includes 10 different engines and eight different airframes.
The FAA’s Lirio Liu, EAGLE executive director, reported that on April 10, 2024, UL100E successfully completed a 350-hour engine durability test.
“Three more tests are scheduled on different engines,” she said, noting the FAA expects the testing to “culminate in a full fleet approval in 12 to 18 months.”
FAA officials note that UL100E has completed about 5% of its detonation and performance testing, 25% of its durability and performance testing, and 20% of its materials compatibility testing.
LyondellBasell/VP Racing has produced about 50,000 gallons of UL100E for FAA testing, officials added.
The other fuel candidate going through the PAFI process, from Phillips 66, did not pass the third phase of testing when “deposits and significant signs of preignition were found,” she said.
Phillips 66 has paused its testing in PAFI, but is still pursuing an unleaded avgas, she added.
Meanwhile, the unleaded fuel from General Aviation Modifications Inc. (GAMI), known as G100UL — which received approval through the Supplemental Type Certificate process in September 2022 — is now available for sale.
More than 1 million gallons of G100UL have been produced by Vitol Aviation.
Swift Fuels, the other contender in the unleaded avgas race, also has received an STC for its 94UL fuel and is going through the approval process for its 100R.
Once that is approved, Swift Fuels President Chris D’Acosta said the company will phase out its 94UL fuel.
He noted that 100R has already completed 400 hours of endurance testing.
What’s Next
While fuel testing continues, EAGLE officials are looking to the other three pillars of the initiative: Supply chain infrastructure and deployment; research, development, and innovation; and regulations and policy.
On the supply chain, which includes fuel producers, distributors and FBOs, EAGLE has already surveyed distributors “to see what the challenges are,” said the FAA’s Ryan Manor.
Next up will be surveying the producers.
Top challenges already identified include maintaining the availability of 100LL during the transition, as well as ensuring the compatibility of all the unleaded fuels, he said.
“This is complex,” he said, noting decisions on the state and local levels — such as attempts to ban 100LL — create additional challenges.
EAGLE officials noted it is imperative that 100LL remains available “until we have an unleaded alternative.”
Another challenge to the transition: The market size of avgas.
Will producers want to get into the business when the demand for 100LL is now about 180 million gallons a year?
To put that in perspective, the demand for automobile gasoline is 135 billion gallons a year.
FAA officials reported that 100LL is produced in just seven refineries in the nation run by four companies, noting a refinery in Minnesota stopped producing 100LL in 2023.
And what about FBOs?
EAGLE officials report that 3,500 FBOs sell 100LL today and these companies will need to make some decisions about adding the infrastructure for an unleaded fuel — either a new tank or a dedicated fuel truck — as well as dealing with other concerns, such as misfueling and insurance.
And then there’s the aircraft owners and pilots. Each will have to make a decision when they will transition to unleaded fuel.
Right now, mogas is available in 180 locations, while 35 sell Swift’s UL94.
To use mogas, the Swift fuel, or GAMI’s G100UL, aircraft owners must buy an STC.
To complicate things even further, the STC process only applies to certified aircraft. There will have to be another process for homebuilt and experimental aircraft, which make up about 18% of the more than 222,000 general aviation aircraft in the United States, according to EAGLE officials.
“Market acceptance will be driven by individual decisions based on many different factors,” they said.
One of those factors will be whether an aircraft will have to be modified to use the new unleaded fuels.
“We know that 2/3 of the fleet should not be impacted by the transition to unleaded fuel,” said Lycoming Engines’ Jennifer Miller. “We do expect a portion of the fleet may be impacted by compatibility issues with unleaded fuel.”
She points to valve recession issues seen with the fleet at the University of North Dakota (UND) after using UL94 for just a few months.
Lycoming, UND, and Swift Fuels are working to “isolate the cause” of the valve seat recession, with an initial theory being that it is related to the aromatics used in the fuel.
“The bottom line is that any learning is a gift,” she said. “The sooner we know about a problem, the sooner we can respond.”
On the regulatory side, the FAA is dealing with having its “new authority” to regulate the composition of fuel, according to the agency’s Ralph Iovinelli.
“We’re working on the rulemaking now,” he reported. “A lot of details go into informed rulemaking.”
Once those details are ironed out, a Notice of Proposed Rulemaking (NPRM) will be released and the public will get a chance to comment on it. Once the comments are reviewed, a final rule will be issued.
While the race to find an unleaded fuel for general aviation was spurred by the Environmental Protection Agency’s October 2023 determination that lead emissions from aircraft could possibly “endanger public health and welfare,” the EPA will play no part in developing or approving the new fuel, FAA officials noted.
As the update wrapped up, FAA officials noted they are working “as fast as we can” to make all of this happen.
“There are a lot of activities going on and a lot of questions,” Liu said, “and a lot of aspects still left to do.”
“As you can see, this is a very complicated process from the refiners to the wing of an aircraft,” added Curt Castagna, co-chairman of EAGLE and president of the National Air Transportation Association, which represents companies that provide a range of services to the general aviation industry, such as FBOs.
What Does All Of This Mean For You?
While the industry and regulators go through the necessary steps, what do aircraft owners and pilots need to know?
Once the LyondellBasell/VP Racing fuel is approved, all you’ll need to use it is a placard and an addendum to your POH.
If you want to use either mogas, G100UL, or Swift Fuel’s 94UL, you can do it now with an STC.
For more information: FlyEAGLE.org
Hi Janice, Thank You.
Good article helping us all keep up to date with the ongoing Unleaded Avgas Fuel developments. Very informative.
One issue that needs to be fact checked.
The publicly provided statement that Lyondell VP Racing (UL100E) has developed a “drop in replacement” Unleaded Avgas fuel for 100LL may not be totally accurate.
It seems you may find their fuel will not cover the entire GA fleet of aircraft engines in use.
Rumors are out there that their fuel will NOT be eligible for use in some high powered Radials and opposed reciprocating engine models (w/o Ops changes or mods needed?).
Please do your best to confirm or deny the accuracy of these rumors.
Regards,
Interested Private Pilot and (A&P)
There’s another challenge of there. I just bought a rebuilt Lycoming O360-C1F from a major and very reputable engine builder. It was frightfully expensive. The warranty for my new engine is voided if I use any unleaded fuel. That prohibition doesn’t make any exceptions for FAA blessed fuels. I’m willing to burn a fuel that is better for the environment, but not if that move will void the warranty on this incredibly expensive motor. What’s a butter supposed to do? Still the FAA cover warranty repairs to my motor if I switch to their unless fuel when it is approved?
Once the right high price for 100 unleaded fuel can be forced on everyone, everything will fall into place immediately, watch !!! I’ve been saying this for years, It’s all about money, good old American way !!!
EPA and the Greenies: SMOKE AND MIRRORS!
I’m not a believer in the EPA.. It’s a huge con for everything.. and people working for them are all heveyly invested in all the products they demand on the manufacturer to purchase to comply with the so called EPA.. global warming is all BS.. MAN can do nothing about the SUN and it’s behavior.. MAN can do nothing about the EARTH’S rotation and tilt as it moves around the SUN.. IT’S been doing the same thing for EONS.. AIRCRAFT are a speck in the atmosphere for the amount of so called pollution they inject into the huge expance of our atmosphere.. I’ve been around aircraft most of my life and I’m still alive at 81 years old..
Has the FAA considered that all GA flights are not necessarily “local” flights but involve cross country trips requiring refueling at remote locations? FBO’s certainly won’t pump all brands of unleaded Avgas so will GA aircraft ultimately need to comply with all of the various use-licensing requirements?
There is no such thing as a drop-in 100LL replacement! After 70 years of many trying, nobody has been successful and I don’t believe for a second LyondellBasell/VP Racing’s works. Has about as much credibility as the Covid vaccine working. See the UND results. 350 hours of testing is nothing. When they test 100 engines for 10,000 hours each, they can report back. It’s not just the effect of running an engine, it’s also the effect of soaking the entire fuel system for years – valves, pumps, hoses, tank sealant…100LL works great, leave it alone. Don’t take the green bait, the day LyondellBasell/VP Racing is approved the EPA will condemn it and demand it be replaced with something until our engines run on water or GA no longer exists. Call your local federal rep and fight to keep 100LL.
The entire idea of putting a date on any “get the lead out of fuel” is pretty funny. I don’t think anyone has hit any planned date on any new aviation fuel substitute in the last 40 plus years.
Nice to see that,” the EPA will play no part in developing or approving the new fuel, FAA officials noted.”The fewer “agencies” involved the better. The issue about leaded AVGAS was already being talked about in the ’70,s when I first started flying, maybe it will now finally happen before I die.
“To complicate things even further, the STC process only applies to certified aircraft.”
Experimental aircraft are also certified, just not TYPE certified.
It seems EAGLE continues to ignore the elephant (G100UL) in the room that already passed all the testing needed and does not require separate infrastructure, according to GAMI.
The drop-in replacement has existed for nearly a half century. It is called Mogas, lead-free, ethanol-free, gasoline, available at nearly 17,000 sellers at prices far below 100LL or its boutique alternatives. See pure-gas.org
MOGAS cannot be used in high compression or turbo/supercharger equipped engines. There are a lot of them out there.
MoGas works just fine, thank you, and is “required” for use in Rotax 912U engines at 10.8 : 1 compression ratio (which SAE considers to be high compression).
Try it in a Sikorsky S-58 with a shaft drive version of a Wright 1820. They suffered a loss of 300 HP just in changing from 100/130 to 100 Low-Life.
The “it works for me so who cares about the rest of them” comments continue. GA is such a small community, we really sell ourselves short when we subdivide into these little groups.
Please note, I currently own a plane that could use the ethanol free MOGAS but I’m not selling my fellow GA owners out over a partial solution. Plus, who knows the next plan I own may not be able to use ethanol free MOGAS.