GAMI Unleaded Avgas Approved For GA Piston Fleet (Updated)

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In a first for the aviation industry, the FAA has approved supplemental type certificates (STCs) for the use of General Aviation Modifications Inc.’s G100UL 100-octane unleaded avgas in all general aviation piston aircraft. GAMI co-founder George Braly stated that the fuel will initially be produced in small batches while the manufacturing and distribution infrastructure is established. Although pricing for G100UL has not yet been determined, Braly noted it will cost “slightly more” than 100LL until production volume increases.

“This is a big day for the industry,” said Braly. “It means that for a lot of our general aviation communities, and especially for a high fraction on the West Coast, relief is on the way. And it means that our industry will be able to go into the future and prosper, and provide the essential infrastructure for this country for everything from Angel Flights to critical training of our future airline pilots.”

As previously reported by AVweb, the new STCs come after significant controversy surrounding the approval process including unanticipated delays and additional reviews. GAMI received its first STC for G100UL in July 2021 and STCs for around 600 additional engines the following October. The company began work on G100UL in 2009.

Braly said the expanded STC covers all of the spark ignition engines (including airframes) in the general aviation fleet. If field experience reveals any oversights, the FAA has agreed to allow amendments through Designated Engineering Representative signoffs.

G100UL will require an STC, which Braly said will be available through a web store the company is setting up. Prices haven’t been established yet, but he expects them to be similar to those charged for the Petersen autofuel STCs, which typically vary by horsepower between $130 and $500, but more for some engine models.  

Production details remain to be determined. GAMI has a production distribution agreement with Avfuel to manufacture and distribute G100UL. Avfuel says it will engage with any refinery qualified to manufacture the fuel. Avfuel’s Craig Sincock said last year that developing the market will take several years.

Initially, Braly said, California Aeronautical University in Bakersfield, California, has agreed to be a launch volume customer for G100UL. Fuel components will either be shipped in and blended or a finished fuel will be shipped from a refinery in Texas by rail.

G100UL’s approval culminates nearly 13 years of research and testing that began shortly after the EPA announced gathering research on leaded fuel emissions near airports. It’s widely believed that the EPA will announce a finding of endangerment on leaded avgas before the end of the year. It’s unclear if this would bring other players into the 100-octane unleaded fuel market. Swift fuel has been selling 94UL for several years and the University of North Dakota had adopted it as its sole piston fuel. Swift is working on its own 100-octane unleaded fuel.  

Braly credits AOPA’s Mark Baker with pushing the FAA to remove barriers to the expanded STCs for G100UL. Although he was not openly vocal, Braly said Baker worked behind the scenes to encourage the FAA to complete the project.

Co-authored with Paul Bertorelli.

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Kate O’Connor works as AVweb's Editor-in-Chief. She is a private pilot, certificated aircraft dispatcher, and graduate of Embry-Riddle Aeronautical University.

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85 COMMENTS

  1. Made of unaffordium just like leaded Avgas. Mogas and Jet-A Burning Diesels are the future for piston power. Produced globally in vast quantities for vehicles and made from the most renewable source imaginable – dead plants and animals.

      • It would probably be less expensive to purchase a piston aircraft with the Jet A fuel engine as standard equipment. Does anyone know why Cessna canned the Jet A Skylane? There ain’t much doing with the Skyhawk model, either.

        • The diesel Skylane on my field was in the maintenance shop sans cowling more than it was in its own hangar. In fairness, anything new will have teething pains; but diesels are on the chopping block in land-based vehicles due to particulates. Many European cities are banning diesels, and natural gas-fueled engines seem to be what Cummins is betting on. As a diesel fan, I don’t like it, but that’s the world in which we live.

    • There is no question that SAF (sustainable aviation fuels) are part of the future. However, the superb efficiency, performance and power to weight of a high performance piston engine solidly has it’s place in General Aviation. BSFC can be 0.38 pounds of fuel per hour per HP produced, in a lightweight and simple powerplant, such as the Continental IO550. At about 3/4HP per pound, only turbine engines with double the fuel burn per HP produced do better. The turbo diesels are only 0.4HP per pound, and are not significantly better with regard to mass of fuel consumed, as Jet fuel is considerably heavier than Avgas.

  2. I’m surprised. It will be interesting to see how long it takes for production to ramp up and the fuel to become generally available. It will also be interesting to see how long it takes for the FAA to approve the other developers’ fuels.

  3. I agree somewhat with Kent. Jet A, diesel, and Mogas would be nice but the reality at present is most of the fuel nowadays is burned by planes that require Avgas.

    This is a big deal and I’m frankly surprised. After so many years I’ve all but abandoned hope for a solution.

    20 years ago, when I bought my Maule, one of the reasons I chose the )-360 was the STC for Mogas. Even then I planned for the failure of Avgas.

    I’m all for using it while we have it and I think we should drill and process crude oil until it’s gone and technically Kent is correct, oil IS renewable, but the time frame means that property is not relevant for the duration of man’s stay on Earth.

    • Also, the phase-out of petroleum-based fuels–or at least avgas as we know it–is probably inevitable at some point in the future, but that future isn’t anytime soon. We’ll need a 100LL replacement before we need a replacement for avgas as a whole.

  4. So…when G100UL fuel shows up at the local airport pump…. Just WHO is gonna pay any attention to the fact I pump it into my little puddle-jumper despite the fact I didn’t bother to pay any money on an STC? Huh? …. Who? (and don’t start yelling the FAA is because they don’t have the time, resources, or manpower to monitor gas pumps.)
    IF the new fuel is “FAA Approved” for use in airplanes without any modifications ….then exactly WHY would anyone send money to the “STC-Holder”.. for a piece of paper that declares the fuel to be universally safe to burn?

      • Oh Jeesh…. another “Insurance Underwriters are the Real Regulators” argument…ad nauseum…
        Besides…..They’d have to prove that the USE of that fuel was the CAUSE of the accident.
        The point isn’t that I plan to cheat (because I don’t plan to act irresponsible OR illegal)…. my question is HOW will they enforce users to purchase the STC prior to using the fuel? What if that new fuel is the ONLY fuel available on the airport…? And what about the Loss of Privacy involved if one has to enter personal or identifying information simply to buy fuel…?
        My airplane doesn’t need the lead…. Just let me choose if lead is added to avgas AT THE PUMP….I’ll choose without lead and I’ll be happy.

    • At our airport, for the 94UL fuel, you put in the STC number for your AC along with other info such as N number otherwise the pump for unleaded does not turn on. I does link that info, your name and the N number to your CC number after the first time. Use a different CC then you need to put the info in again.

    • Yep. And because it is the right thing to do, even though I could probably get away without buying it. I suspect most will do the right thing. And those who don’t are probably skimming free Wi-Fi off their neighbor…and there’s no fixing them.

    • You should buy the STC because the money goes to GAMI and the guy that made this happen. George spent untold amounts of his own money developing it. He deserves to get paid back for his investment in time and money, plus some.

  5. This ensures the future of high compression avgas engines for which there had to be doubts about long term viability. Kudos to Mr. Braly and the GAMI team. It’s great to see innovation and dogged product development of this kind succeed!

  6. So…just to confirm, the 9:1 high-compression pistons on my Mattituck O-360 made me ineligible on the 2021 G100 AML (SE01966WI), but now the FAA says I’m good, right? Will there be an updated AML or does the “all general aviation piston aircraft” save them the trouble of putting one out? Thanks for patient answer(s)!

    • According to what George Braley has said, the extended AML is already complete. It was completed prior to their last application to the FAA for the STC to be issued. I would expect that it will be available on their upcoming website so that your STC paperwork will be specific to your engine and aircraft. As for EAB application, if you are using a Lycoming or Continental engine, it is likely included in the list of engines on the AML. What has not been mentioned that I know of, is where Rotax engines fit in all of this. Rotax are approved for auto gas or 100LL, but I am assuming, to be legal, they would need an STC to qualify for G100UL. Basically an FAA paperwork thing.

  7. When 82UL avgas was “introduced” some 15+ years back (I never have seen it for sale) everyone that already had an autofuel STC was automatically approved to use it. EAA and Peterson sent out new fuel tank stickers to everyone that had their STCs. I have one plane with the EAA STC, and another with the Peterson.
    Will this be the same for this fuel, or will those of us that have an autofuel STC have to purchase this new STC to use it? Then if Swift Fuel becomes more widely available, will you have to have that STC also???? I can see the tops of my wings covered with stickers….

    • That is one reason why the FAA was resisting the use of the STC process for approving G100UL. They wanted it to be approved as a fuel for all aircraft, like 100LL, which is why they went through the PAFI initiative and now the EAGLE program. However, since GAMI declined to participate, the STC was their only alternative. Perhaps at some future point, if the G100UL rollout is successful, the FAA may issue a blanket approval for all spark ignition engines as 100LL currently has. Stay tuned…..

    • No new factories will need to be built. All of the components for the fuel are readily available, mostly from existing refineries and some from specialty chemical producers. Distribution and transportation will be the main problems until it becomes more widespread. As Paul B. speculated, when G100UL becomes more widely accepted, additional refineries, who do not produce 100LL, may choose to begin producing it since it avoids the segregation issues with leaded fuels. At the FBO level, users can simply switch to G100UL in their existing tanks since it is totally mixible with 100LL with no adverse effects. Over time, any residual lead will eventually drop to an extremely low level. Unless the EPA mandates new tanks or a special cleaning process, there would be no reason for installing new tanks and or piping. The only change might be to adjust the metering system to reflect the different density of the unleaded fuel for pricing purposes.

  8. I think that Paul Bertorelli deserves more credit than Mark Baker.
    He wrote some great explainations of the details of the situation that probably got a lot more attention than other proponents.
    Thanks Paul,

    Hope this G100UL works out for GA economically.
    Time’ll tell.
    The trend these days is to use any change on any commodity as an excuse to raise prices higher than the roof.

    • I’m a quarter inch away from not renewing my AOPA membership. I’m tired of invitations for credit cards, frantic emails needing money, daily emails that are OLD news compared to other outlets, and Mark prancing all around pretending to be EAA. They need to reconstitute the Wine Club … oh, never mind.

      PB’s videos will become the preeminent example of video work, IMHO.

    • YES!
      Paul’s rhetoric is likely responsible for the majority of this win. I am sure Mark Baker was taking heat for the piss poor coverage of this issue. I got no positive response from them regarding the gross errors they published regarding Swift UL94 “you need an STC, bla bla” when you don’t if you have a 91/96 or lower octane requirement in the type certificate.
      The FAA should pay for the STC for those 100LL aircraft that require an STC.
      I non renewed my AOPA membership in March, after 30+ years. I don’t think I will go back there.

      • “I non renewed my AOPA membership in March, after 30+ years. I don’t think I will go back there.”

        You may want to re-think that decision. In the video George Braly says “…I want to specifically mention that the the members of AOPA that have provided their dues and their other financial support and donations, that their money to AOPA has been really well spent and and it’s some of the best dollars they’ve ever spent because of the support that we’ve had from Mark Baker and AOPA.”

  9. I don’t understand the marketing plan. GAMI plans to persuade airports to switch to a more expensive fuel, in a world where iPads allow price comparisons – and to do this knowing that each potential customer will have to stop at the pump, dig out their phone, and pay $500 for the right to use the product?

    Give away the STC: heck, e-mail one free of charge to every aircraft owner in the registry. Get a royalty on each gallon sold. That gets you a) universal awareness b) zero speed bump for potential customers and c) lower barrier to adoption by airports, who will dislike the price but hate the speed bump. Yes, it will still be more expensive: that alone could kill the product everywhere that local regulators don’t require it – but if the difference is small enough it might not: there’s maintenance value in eliminating the lead.

    There’s another problem with the “make the money on the STC” plan. Airports have only one tank for 100 octane. Pilots facing a pump with G100UL are going to just use it, creating many, many out-of-compliance situations – unless GAMI plans to require expensive modifications of the pumps (this just keeps getting worse). Creating a lot of non compliant aircraft just can’t end well.

    Give away the STC, proactively. Smaller piece, bigger pie.

  10. Congratulations to GAMI!
    The two questions I have, or at least wonder about are:
    How much money has GAMI invested in the G100UL project so far? With no ROI as of yet.
    And now that the STC has finally been approved, when will we see a clean-shaven George Braly?

  11. Great news, and it’s about time. I agree about Paul Bertorelli’s contribution toward getting it done. The UL issue had been in the spotlight on and off, time and again, but Paul turned on a floodlight. More people were able to get a much clearer and more comprehensive view of the issue and the progress to that point. So congratulations to Paul Bertorelli as well!

  12. Like everyone else, I’m waiting to see how much more this new fuel will cost. I understand the boutique nature of avgas, but am hoping that its ability to go through pipelines (which 100LL can’t due to its contaminating lead content) will eventually mean a reduction in retail price from what we’re paying now. Fingers crossed. At any rate, I’m shorting Innospec now.

    • GAMI’s new fuel will not be sent through pipelines either. It will be moved by truck or rail, as explained by Paul B. in one of his excellent videos. It has nothing to do with the presence or absence of lead, but with the logistics and methods used for transporting large volumes of fuels by pipeline. Since both 100LL and G100UL are moved by truck and rail, the cost of distribution will likely have no effect on its retail price.

  13. Quoting the article: “It’s unclear if this brings other players into the 100-octane unleaded fuel market.”

    This refers to potential FUTURE event(s). The future tense of “bring” is WILL BRING, not “brings”.

  14. ” STC Prices haven’t been established yet, but he expects them to be similar to those charged for the Petersen autofuel STCs, which typically vary by horsepower between $130 and $500, but more for some engine models. “

  15. There are still lots of questions surrounding this fuel. The FAA has no capability to test this fuel, so how was its compatibility with avgas engines determined? How was it tested? What is it made of and what are the other factors affecting its use such materials compatibility, storage and toxicity? Avgas has a published specification. Does this? Who is going to make it and where? Price is the least of your worries compared to the other factors.

    • There have been multiple articles over the past decade anwering those questions: G100UL formulation, testing protocols, results, etc. Usually with the FAA repeatedly moving the goalposts as GAMI met each objection (“Oh, you passed that test? Hmmm, how ‘bout THIS? Did you think of THIS? Oh, you did…. Well, then…”.)

      This video by George Braly has a brief summation of some of the test procedures:
      https://youtu.be/zn4IU87CEMo

    • There is no government “specification” for 100LL. It is an ASTM standard that the FAA requires any maker of avgas to comply with. George Braley has published a similar specification for G100UL so that any company who desires to produce it can do so by adhering to the spec. GAMI has one of the most sophisticated engine test cells in the country at their facility in Ada, Oklahoma and they have done all the various detonation and compatibility testing using their two high performance engines. George went through seven major presentations with FAA subject matter experts who pretty well covered all of your issues and more, and was able to satisfy each group. The concerns that the FAA home office types voiced at the announcement of the EAGLE initiative had already been addressed in those seven meetings. It was a simple red herring so that they could get funding for yet another waste of taxpayer money.