G100UL Triumphs: Now The Hard Part


I could reach for metaphors involving dogs catching cars or irresistible forces encountering immovable objects, but I’ll just go with a simple fact: After nearly 13 years of trying, GAMI finally has a fleetwide STC for its 100-octane unleaded aviation fuel, G100UL. Mark the historic date as Sept. 1, 2022.

Now comes the hard part.

Gaining the approvals is one thing, but manufacturing and fielding a new fuel in a market not yet sure if it even wants such a thing is something else entirely. There are substantial barriers to overcome and if they’re to be worn down, as FAA resistance eventually was, it will likely be many months more, not just weeks.

First, credit where it’s due. We got here because George Braly and Tim Roehl took the EPA’s rumblings about legislating against tetraethyl lead in 2009 seriously and launched a competent research effort to confront it with an unleaded fuel. Ironically, it may have been a premature bet because by the time the EPA has rules in place, it could be 2026, 17 years after the fact. Maybe longer. By then, unleaded avgas is likely to be significantly fielded.

During the decade-plus it took to do this, Braly and Roehl plugged along with purposeful, creative research animated by a unique capability: It was engine-cell centric. Think of this as the fuels equivalent of rapid prototyping. The oil majors lacked this capability and the FAA’s technical support in this realm was mediocre at best. As I pointed out in my video series on leaded avgas, the majors were blasé about research, partly because there was no prohibition against lead, they were making money on 100LL and everyone knew that the FAA’s insistence that an unleaded fuel behave exactly like a leaded fuel was a non-starter. Inertia is its own reward.

Agency sabotaging of GAMI’s efforts was largely a headquarters and division thing, especially the Engine and Propeller Directorate, which deserves special demerits. According to GAMI, staff work at the Aircraft Certification Office level, especially in Wichita, was efficient and professional. From the outside looking in, the test program looks reasonable within the constraints of time and budget. We might have all liked a long-term fleet trial, but that’s going to happen in the real world.

The politics of this effort defy description. Industry players such as Lycoming and Continental were either disinterested or oppositional to the GAMI STC. Cessna was, at best, non-committal, although Cirrus participated in testing and maintained a supportive stance. The alphabets have never been enthusiastic, but against a tide of general resistance, AOPA’s Mark Baker recently worked in the background in support of the STC. And still, there’s a rearguard. GAMA’s press release on the GAMI STC reads like it was dictated through gritted teeth, making progress feel like it’s pulling same.

I suspect elements in the FAA will continue to oppose this STC for manufactured reasons. At the last minute, there was an FAA attempt to impose onerous test and monitoring requirements on the fielding of G100UL, since dropped. I can’t imagine the internal FAA politics here and I’m eternally grateful I don’t work there. But Lirio Liu, the new head of FAA certification, certainly knows the terrain and scythed through it in short order. After a final cert meeting in Oklahoma in August, she promised action in two weeks.

She delivered.

Now Avfuel has to do the same. GAMI has contracted with the company to manufacture and distribute G100UL. Avfuel has done this sort of thing before, but the territory and economics here are incognita. G100UL is a blended fuel consisting of a high-octane alkylate base, plus a proprietary additive package. This can be done in a refinery, but is more likely to be splash blended in facilities capable of bringing the refined components together via barge or rail to complete a finished fuel.

Like everything else in the current economy, rail cars are hard to come by, wharfs for barges are in short supply and transportation is widely more expensive. Avfuel will have to find facilities capable of pulling this together and cut the sort of deals oil companies have done with each other since the days of Standard Oil. It would help if a major got interested in a licensing deal with GAMI and I suspect this will happen sooner than later. Watch for an announcement.

And even at that, G100UL will be selling into a market where 100LL will be cheaper by an unknown amount probably around 50 to 80 cents. Suppliers and FBOs will have to be either convinced of its benefits or within earshot of the proverbial voice of the customer expressing demand. This is not going to be an overnight transition. Avfuel has been saying as much.

One other bit of good news here relates to a GAMI competitor, Swift. The University of North Dakota recently announced that it will transition entirely to Swift’s UL94; it has no need for 100-octane fuel.  This will provide a perfect laboratory to show if the true benefit of unleaded fuel—lower maintenance costs and longer-lasting engines—is real or just marketing babble. UND uses 700,000 gallons of fuel a year and keeps good records. This time next year, we should have our answer. GAMI has a launch customer in the California Aeronautical University at Bakersfield. It’s a smaller fleet, but should yield useful confirming test data.

That’s important, because there is some risk here and no one should pretend there isn’t. GAMI’s test program was as thorough and competent as time and money allowed, but there can always be surprises and if they’re lurking, long-term fleet use will reveal them. This is the benefit of a slow rollout. Sometimes even the blind GA squirrel finds a nut.

Then there’s California at large. And Chevron. Local jurisdictions in California have been making noise about prohibiting lead in fuels for environmental health reasons that the data simply does not support. If that happens or the entire state outlaws lead precipitously, we have a two-pronged problem. Avfuel et al. might not be able to ramp up production fast enough to meet the demand, so the lead deadline matters. Further, Chevron’s Richmond refinery supplies the entire West Coast, including Canada and Mexico, with 100LL. If California decides to ban TEL, will Chevron have the stomach to challenge it or just license refine G100UL or another unleaded fuel? Or simply exit the business? No one has the answer to this because no one knows either a potential timeline or what Chevron’s interests are. 

And last, EAGLE, which is looking more like a turkey at the moment. This is, of course, the FAA’s multi-year program to find and certify an unleaded fuel. In my view, it was a dead letter from the start or, to be fair, the testing component of it is. That’s just PAFI again. But that’s not to say the FAA shouldn’t have a role in encouraging competitive fuel development. But EAGLE has too many players, has overcomplicated the task and assigned testing to the FAA. In my view, this is exactly backward. The industry won’t admit it, but this is the functional equivalent of Boeing or Airbus submitting airplane designs to the FAA for testing, approval and selection.

It doesn’t work that way. The airplane companies do their own testing, supervised and approved by the FAA. Fuels should work the same way. If a BP, a Shell or a Phillips proposes a new fuel, they should also propose a test program that’s a roadmap to approval. The Wichita ACO knows how to do this, as should be obvious. They can’t cut and paste GAMI’s proprietary test protocol, but they’ve got recent experience on overseeing fuel certification. They know what questions to ask of an applicant. It makes no sense for FAA HQ to reinvent this, only with input from dozens of players in a cumbersome, expensive program that seems as likely to fail as the ill-starred PAFI did. It’s in the industry’s interest to have competitors to G100UL if any companies want to step up. But they should do it with their own money, as GAMI and Swift have done. We’ll see if any go there. The first step toward success would be realizing this shouldn’t be as hard as EAGLE makes it look.

In the meantime, when and where can you buy G100UL for your airplane? The best answer is somewhere, eventually. And that’s just a hell of a lot better than it was three days ago.

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  1. I propose a “Bertie” award, for outstanding contributions to General Aviation.
    The first awardee?
    Why, Paul Bertorelli, of course.
    Thanks, Paul, for all that you do for G.A.
    You are a giant among the rest of us.

  2. We could have had cheaper/cleaner 94 UL some 40 years ago (but having more than 1 AvGas pump is also a distant memory). I find it hard to celebrate the same lazy “one size fits all” mentality for GA. I’ll remember the date as adding another $50 for a top off. Great writing almost suckered me into thinking that I should be greatful for what I don’t want, don’t need, and happy that most of the small GA fleet was once again ignored.

  3. The one and only reason that 100LL hasn’t already been banned is that up until now there was no alternative.

    As for California, the state has banned new internal combustion cars as of 2035 even though the state neither generates enough electricity nor has anywhere near enough charging stations to support such a move and hand waves away such objections. 17 other states are likely to do the same.

    You can expect a ban on 100LL in the very near future and there will not be a 13 year period to switch as from the point of view of the state all the industry has to do is stop making 100LL, start making something else, and use the existing distribution infrastructure.

    • Along with what you’re saying Jim. I wonder how 100LL would do if put through the same test as these other fuels are and would it pass the tests? Or even be considered?

      When they switched our fuel from 100/130 way back when, our commercial fleet had all kinds of issues leading to serious consequences. We had to take on a different operating procedure to prevent sticking valves, rings and sludge build up. 100LL took out AvMobile’s fully synthetic aircraft engine oil. Wouldn’t it be nice to use a modern fully synthetic oil? Eliminating 100LL from the industry can’t happen soon enough.

    • California will have a very large fleet of gasoline cars in 2035. If this B.S. holds, I suspect there will be conventional dealerships just across the state line at every major highway.

      • Maybe so but they’ll disallow anyone from licensing a vehicle when it’s new AND for a period of time after being acquired new. They’ve already done that.

        EV’s for thee and ICE’s for the governator, et al 🙁

        • During the Clinton Administration when people began to flee Kalyfornya for places like Nevada, the CA Franchise Tax Board actually used strong arm tactics and intimidation trying to get people who HAD worked in CA but retired and moved away to pay taxes in CA even though they were no longer residents. You know … “taxation without representation.” Pres. Clinton and the Congress actually passed legislation that said that YOU — the person in question — determines your domicile and therefore your tax situation.

  4. I attended George Braly’s forum at Airventure. At first, he wasn’t there because — apparently — he was testifying via video (?) on the subject. Tim started the forum and George appeared about 15 minutes later via golfcart. Attendees could ‘feel’ both the frustration and enmity coming from both of them. George was optimistic that final resolution would be forthcoming by the end of August and … it did. SUPERB! I even collected one of his G100UL badges and added it to my 40 years’ worth of Airventure memorabilia. 🙂 Looking at a pic of George 13 years ago and seeing him now says much.

    “Then there’s California at large … ” Now there’s another major hurdle to surmount … the logistics tail, as you’ve described. If those fanatics out there dictate electric vehicles only to almost immediately ask people not to run their air conditioners or charge their eV’s, I shudder to think of how that’ll all shake out?

  5. First of all: Lirio Liu for administrator!

    If the majors want to field a fuel, they should have GAMI test and certify it as an STC project.

    California should drop the excise tax for unleaded aviation fuel. In fact everyone should stop taxed UL avgas for at least 2 years.

  6. “There is nothing new under the sun.” Ecclesiastes. Paul Poberezny told me years ago how the FAA made the EAA’s Mogas STC testing very tough. Some claimed the agency was tougher on the FAA and Peterson Aviation than on Avgas suppliers. The consequence has been a 40-year track record of a safe and low-cost alternative to leaded avgas. It and other boutique fuels will probably be around for those who can afford them, but the vast majority of pilots in the future are going to be using Mogas and Jet-A Diesel as the price of other fuels climb. Those who self-fuel from the over 16,000 sellers of Mogas listed at pure-gas.org can probably also get a refund of the highway taxes on that fuel to lower costs further. All the details on Mogas are at https://www.autofuelstc.com/

    • Many airports prohibit tenants from bringing in outside fuel in containers, and on the east coast, UL94 airports are few and far between. The Mogas STC makes sense in some cases, but in many cases it does not simply because it is so difficult to obtain the fuel in many areas.

  7. I see now how George Braly’s long experience as a litigator was instrumental in buttressing the engineering part of GAMI’s effort.

  8. Paul:

    Another great article. Another point–
    Are we just going to have G100UL nationwide, or do I have to get STCs for 94UL and G100UL. What will the Eagle initiative produce? When we went to 100LL in the 1970s, it was to a universal fuel. Is that where we are heading now? I don’t care to have a separate STC for different airports.



  9. So another market that might make sense for the big refiners to jump into licensing G100UL would be the off highway market. Total sales is over 7 Billion gallons / year with boats and powersports equipment making up about 3 billion gallons of that. Avgas is only about 150 million gallons but it might make sense to formulate, market and sell one type of fuel. The perceived value of “aviation gasoline” might help the profit margin as well. Expanding the potential market by 20x could be a good thing for everybody. I would sure love to run G100UL in my paramotor, side by sides and my race car!
    Data is old (2014) but the numbers make the example valid- https://www.fhwa.dot.gov/policyinformation/pubs/pl17012.pdf

    • We have a local drag strip and drivers often visit the airport to fill up jerry cans of “aviation gasoline”. At least two independent gas stations near the track stock 100 octane fuel.

      Heck, even our local Sheetz is now stocking, I think it’s 94 octane, ethanol free fuel.

      So yes, there may be other niche markets to be captured.

  10. Like many I was surprised and somewhat dismayed when the FAA EAGLE program was announced. I came to see that, as Baker, Bunce and Pelton all said, a primary goal of EAGLE was to establish a firm deadline that was far enough into the future to provide a transition period to a new fuel. I don’t think that was the only motivation for EAGLE, but perhaps EAGLE at least serves this purpose (and can save a whole lot of taxpayer money by scaling back on other goals, although as you write some unknown may arise that requires we have a backup).

    Question: AVfuel is cited as not only distributing but also supplying (i.e., manufacturing) the fuel. There’s nothing about actually producing fuel on the AVfuel website. Is it more correct to say that AVfuel has agreed (with GAMI) to negotiate with fuels manufacturers to produce G100UL?

    Like you, Paul, my biggest concern is the ability to move from an entrepreneurial design/certification mentality to a full-scale business production/distribution capability–and if it can happen quickly enough to avoid more widespread fuel availability issues in California and elsewhere.

    Thanks as always, for your insights, Paul.

    • Agree wholeheartedly. George and Tim’s track record as engineers goes further than just G100UL. What they did for the Beechcraft T-34 after the “fighter pilot for a day” folks ripped the wings off three of them is a story everyone needs to know. They engineered simple but elegant AMOCs that they tested on their own dime and produced data the FAA couldn’t deny. George and Tim deserve every bit of recognition that comes their way. How about it AVWeb?

  11. Paul is accurate with this; and this is the model the NRC uses – which has caused the death of clean nuclear power in the US: “But EAGLE has too many players, has overcomplicated the task and assigned testing to the FAA. In my view, this is exactly backward. The industry won’t admit it, but this is the functional equivalent of Boeing or Airbus submitting airplane designs to the FAA for testing, approval and selection.”

  12. Not to pick nits unnecessarily here, but will application of the blanket STCs for G100UL and UL94 also pertain to engines that have been modified under various other STCs. A popular example is the 150 HP Lyc. 0-320-E3D (found in later Piper Cherokee 140’s and early Warriors) that were modified to 160 HP under a RAM STC. That STC requires that the modified engines use “100 or 100LL Avgas Only.” For this example G100UL might not pose any “STC conflict,” but UL94 might. If the blanket fuel STCs are something less than “blanket,” it would be prudent for operators of all sorts of STC-modified engines to review the fuel requirements specified in their STCs and resolve any conflicts.

  13. There seems to be a lot of exotic chemicals in the GAMI 100UL. I think it is great that there is an approved 100 UL fuel now, however I think I will wait until there is some field experience before putting any in my airplanes.

  14. “G100UL will be selling into a market where 100LL will be cheaper by an unknown amount probably around 50 to 80 cents.”

    Doubtful, more like $3 more for G100UL.

    Read carefully what GAMI wrote about price:

    “Current best estimates are that G100UL avgas will cost 60-85 cents/gallon more than 100LL as the fuel leaves the producer’s facility and begins to enter the stream of commerce. Estimates are based on crude oil pricing at 40-60 dollars/barrel, and will vary with the price of crude oil.”

    Using average numbers from above: $0.73 more with crude oil at $50.

    Crude oil is now $95. That’s a 90% increase. Premium scales with oil prices. $0.73 becomes $1.39.

    The price is “as the fuel leaves the producer’s facility”. That is, wholesale before transportation, taxes, flowage fees, and markup. Those factors will easily increase the premium by 70% and could double the price in some cases. $1.39 become $2.36.

    The estimate above fails to disclose the underlying assumption of production scale. Is this the price on day one or some distant future price after all transition costs have been paid for and the entire 100LL market is G100UL? One can reasonable expect the estimate assumes some scale of production that will not exist on day one, so the price will be higher still.

    The average price of 100LL is just about $7. When G100UL hits the market, I expect it will be $10 if crude oil prices remain the same as today. A $0.50 premium for G100UL just does not compute, the premium is already way over that at the production site.

    Beyond price, the next big question is liability. Who is going to get sued when a G100UL using airplane crashes? It will happen, whether justified or not.

    Things to think about.

    • I don’t see your logic.

      G100UL takes the same amount of alkalyte as 100LL within small margins, so what does the price of crude have to do with it?

      As for other chemicals, it seems like the xylene component should actually be cheaper. Shipping and distribution should be less or the same. And avgas is not made in sufficient quantities to be sensitive to scale effects.

      So the $0.85/gal premium seems to be a reasonable delta to remain.

  15. I’ve heard that G100UL weighs in at 4-6% heavier than 100LL.
    If true then is a GW increase part of the STC?

    • How about a useful load DECREASE? Certificated gross weight can’t be changed just because the weight might be a tad heavier.

      • Lots of STC’s increase GW by 5% as part of the mod. At least that way the new fuel does not have the double-whammy of both higher price AND a useful load DECREASE.

          • Off the top of my head, the O-320 engine STC on the AA-1A to increase GW to 1600#, BRS installs on C182s get a 160# increase in GW, and the myriad of Bonanza tip tant STC’s that increase GW.

    • Assuming 100LL is 6lb/gal, G100UL at 5% heavier would be 6.3lb/gal. At 72 gallons (the capacity of the Dakota I fly), the difference is about 22lbs. Or just over 14lbs at 48 gallons. So yes, you do lose some payload but in most cases it won’t make a significant difference.

      • Do you have any documentation to that effect? From what I’ve seen it’s teh same (or less) energy density.

        • Here’s an AvWeb article from 12 years ago:

          “It’s a little heavier than avgas–6.4 pounds compared to 6.0 pounds–but it has higher energy density so it’s within a couple of percentage points of being a wash.”

          There are no exotic chemicals in G100UL. The BTUs of the constituent components are well known and easily calculated.

          What have you ‘seen’ that says it has the same or less energy density? I suspect the source of such an assertion would benefit from spreading FUD (Fear-Uncertainty-Doubt) about G100UL.

          • But at the same compression ratio and with fixed timing; the power output is going to be the same. They are trying to assert that because a fuel has a higer energy density that the engine is capable of taking advantage of that. Not true at all.

          • But it’s not a static, fixed environment – you still have a mixture knob.

            Piston engines measure fuel by volume, not weight or energy content. The carb (or fuel-injection) presumes each gallon of fuel weighs the same. So if you feed the system with fuel of higher density, in effect you’re putting more fuel in and getting more power out.

            This means if you lean to a specific fuel flow, you’ll find yourself going (slightly) faster on G100UL than 100LL.

            If you lean to a specific EGT or speed, then you’ll find yourself burning (slightly) less fuel while cruising at the same speed.

          • How interesting! Thank you, Kirk, for sharing the link. So it appears that, using an SR22, Gami, as a small business, was getting the job done on our behalf. Meanwhile, Cirrus and parent AVIC (AVIC estimated to have 500K employees) cannot even come up with an approved conversion to install THEIR OWN unleaded engine on the SR series aircraft.
            Read the first paragraph…


  16. Most eloquent paragraph:

    “And last, EAGLE, which is looking more like a turkey at the moment. This is, of course, the FAA’s multi-year program to find and certify an unleaded fuel. In my view, it was a dead letter from the start or, to be fair, the testing component of it is. That’s just PAFI again. But that’s not to say the FAA shouldn’t have a role in encouraging competitive fuel development. But EAGLE has too many players, has overcomplicated the task and assigned testing to the FAA. In my view, this is exactly backward. The industry won’t admit it, but this is the functional equivalent of Boeing or Airbus submitting airplane designs to the FAA for testing, approval and selection.”

  17. I always love the hate-on-California comments, especially by those who use smartphones, the Internet, fly airplanes, benefit from space, eat our food, live longer, etc.

    Really guys… give it up. California banned gas-powered cars. Get over it. In fact, be thankful.

    Yes, it will ban 100LL. Long overdue. Lead falling out of the sky is something nobody should support.

    Californians live longer than anyone else in the US, except Hawaii, and enjoy one of the world’s largest economies, a higher standard of living, and more equality and opportunity than the vast majority of the world.

    Oh, and much of space and aviation is or started here. Edwards, JPL, Mojave, SpaceX (yes, it started here), and so on and so forth.

    Get over it.