NATA Challenges GAMI’s Assertion Of ‘Commercial Availability’ of G100UL


The National Air Transport Association (NATA) says General Aviation Modifications Inc.’s (GAMI) FAA-approved G100UL is not yet “commercially available” even though the licensed manufacturer of the unleaded avgas, Vitol Aviation, has more than a million gallons of it for sale. In a statement, the organization, which represents FBOs and fuel distributors, said that because G100UL has not been granted a consensus standard by ASTM International, it cannot be considered commercially available. “Because the FAA does not indemnify any entity in the supply chain for damages caused by fuel-related issues, fuel distributors and FBOs will similarly lack assurances that the unleaded fuel they are selling will not expose them to liability,” the statement says. “At present, G100UL is not commercially available for distribution and sale in the U.S. largely due to the fact it does not have an ASTM International product specification.”

G100UL has an STC that covers every engine in every certified airplane on the FAA registry. Helicopters will be covered shortly. GAMI founder George Braly has argued that an ASTM specification is not a prerequisite for commercial availability. The opposing positions take on new significance in California where an environmental group is trying to force several dozen FBOs to sell G100UL. The FBOs were signatories to a consent agreement that resulted from a suit by the Center for Environmental Health over leaded avgas in 2018. That agreement compels the FBOs to offer a lower lead alternative for sale as soon as one becomes “commercially available” and the CEH has sent letters to them all saying that G100UL must be offered.

NATA says it has heard from some of those FBOs who have taken the position that because it lacks an ASTM standard and hasn’t been properly tested and approved to be mixed with other fuels, G100UL is therefore not commercially available. “NATA’s understanding is that most distributors and FBOs do not believe that G100UL is “Commercially Available” as defined in the settlement and have provided a detailed response to CEH explaining their reasoning. NATA shares the position of these distributors and FBOs.” The stakes have also been raised somewhat in that there’s a bill working its way through the state legislature that would ban leaded avgas.

NATA is a member of the End Aviation Gasoline Lead Emissions (EAGLE) group and its president Curt Castagna is the co-chairman of EAGLE. The organization held a press briefing on Tuesday updating media and stakeholders on its efforts to find and transition to a suitable unleaded fuel.

AVweb has asked the Center for Environmental Health for comment on the question of commercial availability but has not received a response.

Russ Niles
Russ Niles is Editor-in-Chief of AVweb. He has been a pilot for 30 years and joined AVweb 22 years ago. He and his wife Marni live in southern British Columbia where they also operate a small winery.


  1. “G100UL has an STC that covers every engine in every certified aircraft on th FAA registry.” As I’ve commented on previous stories that have made this error, this is not true.

    “in every certified airplane” would be more correct (and I’m assuming that statement is true).

    • Sorry Steve. I keep doing that. The helicopter STC is in process according to Braly and should be announced shortly.

  2. There is NO WAY KNOWN that I’d be using an avgas with higher than 15% aromatics in any engine that is thermally stressed….. there are a number of reasons for this, and to date I’ve seen absolutely no public disclosure of any comprehensive test data that shows that these ‘new’ high aromatic fuels don’t cause engine damage over the long term in many or even perhaps all of the thermally stressed engines, that incidentally compose around 30% of the air-cooled fleet globally. The potential damage is NOT limited to VSR, and is significant and potentially a risk for continued safe flight from my experience. We’ve been seeing this in a non-USA setting over the past decade in certain types of operation. Additionally, i’ve seen no teardown data for engines that have run to TBO with any of these fuels, when they had been used as the sole fuel for that engine for its life. We have absolutely no idea on how they might impact of durability throughout the full life of the engine in real world operation. I could make you a mix in about a week that would meet the basic test requirements of ASTM D910 (apart from the lead content) BUT there is no way that I’d just fill my tanks and use that in my $100,000+ engines!

    I’ve seen no real world (both ROP and LOP) operational data over a long term when these fuels have been mixed at multiple different proportions with the current approved (leaded) fuel. Make no mistake, there WILL be some surprises here in real world, just like there was in PAFI real world testing after the various offerings looked pretty exciting in highly controlled (mostly indoors) testing.

    I say again….show us the data…. ALL OF THE DATA relating to ALL OF THE DIFFERENT BREWS USED throughout the testing of ALL of the different engines, and then lets see several of them in real world operation in commercial operation running to TBO. I’ll bet none of the offerings are willing to open their doors to an independent body (who knows what they are looking for) and examine all of their test records for the entire development process! So, prove me wrong ‘second coming messiah’s’ and be fully transparent with the OEM’s with the FAA and with the public. I’m also certain that insurance companies will be extremely interested in the FULL picture too. Personally I doubt that we will see a fuel that has proved as good as we’ve had for the past 70 + years in GA.

    In addition, in light of the discovery of the previously seemingly intensionally buried ‘airport vicinity lead testing’ showing either ‘extremely low’, or ‘below detectible limits’ when it comes to lead in the atmosphere, why the hell are we even bothering to change anything. WE DON’T NEED a new fuel, because in blunt reality WE DON’T HAVE GENUINE PROBLEM, yet we are doing our very best (at least some people are) to create a brand new problem.

    Disclosure – been in the aviation fuels business (professionally qualified), the engine overhaul business (professionally qualified), the GA piston aircraft operating business (professionally qualified) for over 40 years, and have lectured on aviation fuels and lubricants to hundreds of licensed aircraft engineers ON BEHALF OF THE REGULATOR in a very large country.

    • I here what you are saying but perhaps if you don’t burn kerosene then, al the levels of government and alphabet agencies, this issue is pretty low priority.

    • Speaking of full public disclosure, “Skygypsy”, who are you and why should anyone take you seriously when you are hiding behind a psudonym? I could make all kinds ouf outlandish claims to my pedigree just as easily as you did.

    • Answer 1: unlike aircraft parts, FAA does not regulate fuel directly, but delegates the fuel oversight to ASTM to ensure adequate peer review and process is followed
      Answer 2: see answer 1?

      Personally I’m a fan of a greater number of competent people checking any new fuel is ok (or understand any new limitations) before I use it. Even if that takes time.

  3. Oh Boy!
    GAMI likely knows more about fuel and has done more knowledgeable testing than any other entity.
    Perhaps the commenter above does know more than George Braly, or not!
    Change is hard for people and particularly organisations; particularly combined with ignorance.
    The nonsense about leaded fuel replacements is just that; nonsense.
    Lead is clearly bad for engines and for people; arguing about just how bad for people is nonsensical; we no longer use arsenic in “cures” because although a small quantity can be tolerated, it is not good for people.
    The amount of foot dragging on this necessary change is beyond belief!
    The other side of it is likely the Tort culture in the US; Lawyers just waiting to pounce on anything new, good, bad, or inconsequential.
    Please ship me the GAMI fuel; I will take it off your hands and happily use it!

    • George from GAMI certainly seems to be informed when it comes to fuel, but I’m sure he’s not the only one and also not the only one to be familiar with testing.
      So independence of testing as well as peer review for such a significant change would be a good thing rather than us relying the assurances of the person marketing a new fuel don’t you think?
      Reading the article, I’m presuming the lack of testing transparency, lack of peer review and lack of clear legal liability (if the testing has proven inadequate) is causing some airport fuel suppliers to think twice. If the testing has not been approved through a consensus body like ASTM (or perhaps EAGLE?) then who is on the hook if there has been a lack of due diligence? It might be that some people are feeling that the market is simply not profitable enough to offset that risk?

    • ASTM not being in the POH is not the control. The legal control is whether the specification is listed in the Type Certificate as an operating limitation

    • In the big scheme of things, so little of the fuel burned world wide is 100-LL, and it seems dangerous to risk engine failure and human lives to switch. What’s the upside… Marginally cleaner burning fuel and happy environmentalists? What’s the downside… Breaking expensive engines at best, or killing pilots and passengers at worst? No thanks.

      • have been an observer of your contributions for approximately a year now, and I must express my profound disappointment in the consistently negative portrayal you offer regarding initiatives beyond the realm of ASTM standards, particularly those related to GAMI. It appears evident to me that your perspectives may be influenced by political motives, as your arguments often lack substantive depth, relying instead on mere assertions underpinned by your personal experience. Regrettably, your discourse is often marred by a patronizing tone, which regrettably does little to foster a sense of community. Consequently, I feel compelled to challenge you on this matter.

        While you’re under no obligation to share more detailed evidence for what you’ve claimed your points would be better made if you provided the technical research or data behind them. Thanks.

        As I understand the ASTM standard for aviation fuel was established in 1947. I’ve also reviewed some of the data sheets for 100LL and there’s enough variation on the data sheets to drive a DC3 through.

        In contrast, my understanding of the data sheet for GAMI 100UL is based on todays manufacturing equipment and procedures which provides for a much more narrow production capability for G100.

        Further, G100UL is here today with over ten years of testing and NO valve issues.

        Your comment seems to provoke a reason to reject G100UL due to the aromatics. Support that statement! I call bs when it comes to aromatics. You allude to the properties of the fuel which will vary in performance based on composition. A fuel having more aromatics will need a chemistry that allows for desired performance. You don’t necessarily say a fuel will never work because of one element. That’s like saying we cant have full fuel today because the air density of too high. AS you should know there are compromises with getting a performance from a fuel. I am surprised you haven’t attacked G100 for being heavier. You’d certainly dismiss the higher energy per volume discussion. While I minored in chemistry I certainly didn’t focus on fuels so I an always open to learning something.

        I appreciate what Mr. Hope shares as it is time for market forces to have a play in this. When NATA comes out to attack G100UL and the principle complaint is that it’s not ‘technically’ a commercial fuel I find that laughable and reaching for any argument.

  4. The supply chain of leaded fuel is unsustainable. End users of 100LL can argue all day about whether there is a health hazard among persons living near airports. But, to make the fuel, the lead has to be refined (or recycled), formulated into the tetra-ethyl lead, transported, and then added to the fuel.

    As an occupational health specialist, I have treated adults for lead poisoning for almost 40 years. I have never seen a lead production system – from raw materials to final product – that didn’t poison someone along the way.

    When it comes to lead, it isn’t just people who live around airports who may be at risk of harm. We don’t get to put lead into fuel without also getting it into the bodies of someone along the way. Like it or not, this battle is over, no matter how much we complain.

    • 40 years of experience or perhaps you’ve got one year of experience 40 times over….. some of your comments here indicate that you have precious little knowledge about things that are outside your specific area of practice.

      • You also claimed 40 years of experience. Maybe all your experience is from 40 years ago? Unleaded auto gas was banned just 30 years ago so it makes sense.

  5. Key take away from the NATA comments: “Because the FAA does not indemnify any entity in the supply chain for damages caused by fuel-related issues, fuel distributors and FBOs will similarly lack assurances that the unleaded fuel they are selling will not expose them to liability,”. That statement is exactly what my FBO manager said in response to my question about selling some of that 1 million gallons of G100UL at our airport. The STC means nothing to them, they are concerned (rightly so) about being sued when someone needs an engine overhaul.

    The change from 100LL to any UL is going to require a government forcing action. As much as I hate do good government actions, I hope CA passes the law on banning 100LL as that will force the change to happen. I looked in my C172 POH and there are only two approved fuels, 100LL Grade Aviation Fuel (blue) and 100 (Formally 100/130) Grade Aviation Fuel (green). There is nothing about an ASTM spec fuel being approved for use, so NATA is blowing a bunch of EAGLE smoke on that factor. The only way to change that is for Cessna to issue an update to the POH for new fuel types (not going to happen, see liability issues above), buy an STC to use another fuel (currently process), or have the government (FAA or congress) authorize/declare the new UL fuels are legally equivalent to 100LL Grade Aviation Fuel with no/any color. As far as I know, the FAA has not said how the fuel type listed in the type certificates for aircraft and engines will be changed to authorize use of a new UL fuel without an STC requirement.

    • ASTM not being listed in the POH does not mean that there is no requirement to have Avgas 100LL meeting ASTM D910. The legal control is whether the specification is listed in the Type Certificate as an operating limitation, not the POH.

    • I couldn’t care any less about the whole “commercially available” spat. In fact, if California manages to get rid of piston airplanes using this “crisis”, it might finally wake some people up.
      I am curious though whether an FBO is actually indemnified or otherwise protected when selling AvGas and how. These aviation lawyers seem to manage to sue anyone with pockets for anything.

      • Old Eric…. diesel cars on the road in LA alone are FAR MORE dangerous to the community than all the the GA aircraft in the world combined. Why do we not immediately ban the sale of diesel and immediately crush all diesel cars. Germany has started the process against these ‘poison pumpers’ by banning the use of older ones in certain areas.

        • I’m sure we can find hundreds of things we should ban before AvGas if it were really about its dangers. I think the lead issue is just used to amp up public support and increase the cost of defending our use of the sky and our airports.

          Still, curious about this whole indemnification argument. Sounds to me like it’s a typical stolen base exercise that is based on BS.

  6. NATA has an inherent and obvious Conflict of Interest and needs to bow out of having an opinion for consideration

    • Please explain, and it will be interesting which ‘conspiracy theory’ you try to air, because you’re utterly wrong Mr Walcott.

  7. Bless George Braley’s heart, initiative, and drive, but I don’t think we’ll see any fully unleaded fuel in aircraft engines in his (or my) lifetime. It’s not a scientific hurdle as much as facing too much institutional and commercial inertia. If the automotive industry is any kind of technological bellwether, it looks like I/C engines will be supplanted by electric powerplants (hybrids are merely a transition solution).

    A little over a hundred years ago, most of the US population depended on horses (and put up with their waste products and high maintenance) for motive force. Then a technology was refined enough to make itself affordable (and just dependable enough) to obsolete the animals in cities, and eventually the entire country. Not to put too fine a point on it, George has developed a new hybrid grain that makes horse-poop not quite so smelly.

    Although we are in the very earliest days of applying electric technology to aircraft (or boats, or lawnmowers for that matter), it seems to have the least “unintended consequences” of any of the energy solutions on the horizon. Storage density and proper disposal are the major issues, but you know that physicists around the world are tweaking their AIs right now, looking for solutions to those issues. When I was a kid, my first flashlight (a special “Boy Scout” edition) was a heavy WWII-vintage D-cell monster that could be used to pound tent stakes in a pinch, but would not last a weekend of nighttime latrine trips. Battery chemistry has come a long way, and shows no sign of slowing down. Internal combustion engines, as we know them, are following the coal-fired steam engines into the museum realm of technological curiosity.

    In a similar vein, has anyone noticed how close we are getting (for better or for worse) to the George Jetson model of AI air traffic control in congested areas? Forget ADS/B-out, some of you are likely to see the day that certain critical airspace is limited to R/C-autopilot-equipped airspace, like the DC FRZ or NYC.

  8. We need to transition away from leaded fuel as soon as possible. That said, it is foolish and perhaps dangerous to pilots if we all start using G100UL without a measurable standard such as that provided through ASTM. I sense some resentment to standards as somehow slowing progress, but is the establishment and adherence to standards which lets our complex society run. I prefer the G100UL go through the ASTM approval process before I suddenly and catastrophically experience knocking while leaned out at 16,000’ in my turbocharged Mooney.

    • Good points Scott. I’d be stunned if ANY of the current unleaded avgas will be the fuel that eventually gets approved. I can assure you have NONE of the current offerings even come close to being an ‘airworthy fuel’ for use in carburettor equiped Lycoming engined helicopters operating in hot climates. How do I know? hundreds of thousands of hours of data and thousands of damaged cylinders (neither figure is exaggerated btw) with the use of high aromatic content fuel.

  9. Seems like the most relevant question is, Why isn’t GAMI allowing public testing and ASTM certification? Why are we just supposed to trust them? Is there something being hidden?

    • Hey Avidflyer, that’s a truly good question. I wonder if we can get this to happen, but it would absolutely need to be independently conducted and to TBO in at least 50 different aircraft and helicopters in real world operation and NOT in dynos and under highly controlled conditions. We all know (well those of us with the appropriate lifetime of experience) that many things can be shown to work in tightly controlled environments that simply DO NOT produce similar outcomes when in the hands of John and Jane Doe.

    • “Why isn’t GAMI allowing public testing and ASTM certification?”

      Because the ASTM is not some independent, objective, government body like the NTSB with no skin in the game.

      The ASTM is an organization made up of the same petroleum producers whose sales would be threatened by any new fuel produced by someone else. Although on paper there are safeguards to prevent overt corporate interference, in my opinion the reality is it’s all too easy for established players to put their thumb on the scale of studies and committees and doom any new product to the purgatory of eternal bureaucratic delay.

      Braley saw this early in the process and bowed out, spending his few dollars on fighting the FAA for an STC rather than the ASTM for their blessing.

    • Search for AOPA Gami fuel test. It has some good info. AOPA is testing a twin baron with both fuels. One engine runs on 100LL other on 100UL.
      Youtube has some good videos on that. FAA process alone took 12 years.

  10. Well, I expected this to happen at some point. Now it has. There is no question in my mind that G100UL is an acceptable fuel and I would run it in my engines without reservation. On the other hand you have to pay for the STC to use it. It is sole-source.

    The issue here is political and not technical. Certification of an unleaded fuel was taking so long GAMI took a chance and went the easy way, i.e. STC. They got their fuel approved and the hope then was people would buy it. (I definitely would.) Now the other groups that have skin the game have anted-up and tried to block GAMI until they can get their fuel to market. Now GAMI has a choice: submit to ASTM, let their formula be known, and accept a lower long-term payout (no revenue from STCs), or raise and hope their hand is good enough.

    I really like George Braley and GAMI. I like that they are scientists and engineers who are using scientific method to produce new knowledge from which we can make informed decisions. The naysayers are using FUD to cloud the issue. Regardless, that is the reality of the world we live in. GAMI may have to turn loose of the G100UL formula to ASTM to receive ASTM approval or lose entirely. I hope they win and make a bunch of money but in the end, they may have to bite-the-bullet and accept less in order not to lose completely. Politics sucks and we, the pilots and aircraft operators, are going to be the real losers.

  11. So, Brian, with respect, then you are asking me to just trust GAMI (and George Braley).

    I’d trust more if GAMI would allow other groups to test the fuel (and my understanding is that they specifically won’t). I’d trust them more if they’d provide liability protection (and they haven’t). I’d trust them more if they had enabled testing of G100UL in mixture with other fuels (No idea if they have or haven’t, so, I guess, just trust them)? I’d trust them more if they’d just provide a pathway to certification…

    We’ve had ASTM certified fuels for decades. Certification works. I’ve never thought even once about who blended my 100LL, because it’s standardized. Nor have I ever thought once about it’s effect on my engine, or liability if there’s an issue, or any of that… because it’s standardized and ASTM certified.

    I’ll be happy (really THRILLED) to use any unleaded fuel that gets out there… but there are good reasons it oughta be ASTM standardized. If it’s GAMI fuels, that’s great, and I hope George (and company) become filthy rich. I have no dog in that fight. But, I am very reluctant to just trust… there’s quite a bit at stake.

    My two cents.

  12. I see a lot of people in the comments expressing a need to eliminate leaded fuel “as soon as possible”, and I agree that we should work diligently to find a safe and cost effective replacement. That being said, the people who are in a panic to adopt the first product coming over the horizon are more dangerous than the lead itself.

    We entrust our lives and the lives of our passengers to the proven safety of the aircraft, engines, fuel and procedures that we utilize when we fly. To rashly rush ahead and demand that we be forced to fly with a fuel that has not been vetted any better than Boeing’s MCAS system is a recipe for disaster. I’ve had one engine failure at night over wooded terrain – once is enough.

    For those who believe we need to make the switch this instant or we will all die, let me point out that with or without the minuscule amount of tetra-ethyl lead that we consume, the world’s lead mines produce and refine 4.5 million metric tons of lead every year, and the world consumes 12.65 million metric tons of lead (new and recycled) every year – 86% of which goes into lead-acid batteries. Of those 4.5 million tons mined every year, only 319 go into the US 100LL avgas market (.007%). No wonder the environmental studies around airports found no measurable increase in lead concentrations. Even lead utilized in bird shot and ammunition rates 1% of annual consumption. To equal that we would all need to own and fly 143 airplanes each!

    The amount of lead we save will never be noticed by the environment, our health, or the lead mining industry for that matter. We can afford to take our time to do things right. Has there been anything else lately that the world said we all had to do in a mad rush that now we are regretting? Patience, testing, analysis – let’s please be smart. We do not want Chicken Little in charge of our families’ safety.

    • No…. Flyer Don, the problem is rash…. not hanger rash, but rash. We need more haste and less speed.

      All my comments in the fuel discussions apply EQUALLY to EVERY SINGLE UNLEADED AVGAS. I’m not a fan of any of the formulations, because whilst they will work fine in many engines, my own personal experience is that some machines are most certainly NOT going to be OK, and these aircraft owners must not be just deserted and left with unsafe machines because of the selfishness and rashness of the masses.

  13. All this is great for a stitch and bitch but some very valid points have been brought up and missed. There has been “some” testing of the fuel sim “some engine applications. But there has never been ANY testing in ALL applications. One engine tested in a Piper does not mean it will work in ALL applications of the same engine model. Plus it hasn’t been transported 1000 miles in a truck and pumped into a tank in BFE and left to sit for god knows how long before some unsuspecting pilot pumps it into his airplane and takes off over some mountains at night to see family on the other side. Very few things are worse than a hand grenade failure in that situation. Yes it can happen with 100LL and that has been tested but if you put ANY of these fancy synthetic gas substitutes in your airplane then YOU are the test monkey. End of rant.

    • Agreed. Look what happened with a ‘brand new oil’ when Mobil bought out AV1 back some years ago. A really experienced team from a well known and respected company even… and an oil to replace all that proceeded it, that ended up with thousands of grounded aircraft and law suits all over the world! We didn’t need that new oil and we certainly don’t need any new fuels. Keep with the avgas we know, which through environmental testing has shown that the residues are all but undetectable, and keep our engines running happily to TBO like they have been for the past ¾ of a century! Some day in the future the old Lyco and TCM engines will be replaced with a new technology that doesn’t need avgas. #DropTheUnleadedScam should be the new trending tag.

  14. This is not the big fuel issue. I believe the climate hammer is going to drop on GA with full force sooner than most people think. Protesters chained themselves to my FBO recently and it’s happening around the world. GA, and not just business jets, are a big target. It doesn’t matter that we use only a fraction of fossil fuels burned – what we do is perceived as frivolous and unnecessary by the masses. I’m not an engineer so I can’t comment on practicality issues, but if cars are going electric now, personal airplanes need to as well and as fast as possible if we want to have something to fly. Climate catastrophes are getting worse and at some point, people will demand action. When they do, watch out – things will happen quickly.

    • The electric cars ‘thing’ is already running out of steam, and they are not the long term answer. Don’t be afraid of a few nutters…. if law enforcement doesn’t deal with them, the public will as is being seen more and more often with them being tossed face down onto the bitumen by pissed off commuters….

        • With my crayons and big sheet of paper… I’m saying that electric planes are not in my lifetime and nor do they need to be, the pressure from a few climate nutters won’t change that and the electric car ‘thing’ is already faltering if you look at the stagnation of sales and the canning of models by some big manufacturers. It’s not going to be transplanted into GA any time soon, and I fully believe that other technologies will overtake these absurd ‘battery/motor’ vehicles….. that’s all.

          • Current battery tech is too heavy for airplanes but we do not know what the future may bring. How can you be so sure with your predictions?

            I just googled and 18% of the new cars sold in 2023 were electric. It is a high percentage of “absurd” vehicles.

          • Our friends at Hertz Rentals admit that the EV venture has cost them an estimated 440 million dollars and are selling off/disposing of 195 million dollars worth of EV’s. Go figure.

  15. Ponder this- 100LL came out when VLL red 80/87 was an option at the pump. What would the impact of again halving the lead in 100LL? Good enough for 10:1 N.A. and sensitive turbos, both?

    How about adding lead AT THE PUMP? Dial-A-TEL?

    I run 1/3 to 1/2 90 REC no ethanol, watching seasonal blending issues, a risk, to cut my lead. Engines seem to love it.

  16. NATA President Curt Castagna also EAGLE chair putting a halt on GAMI sounds like a conflict of interest it doesn’t smell right! What’s the real reason I suspect $$$.