GAMI Responds To Cirrus G100UL Service Advisory


General Aviation Modifications Inc. says it will issue a detailed response to Cirrus Aircraft’s recent service advisory discouraging the use of GAMI’s G100UL unleaded fuel in its SR series aircraft. In a statement to AVweb, GAMI said the service advisory appears to be linked to a single incident in which the sealant used in the fuel tank had unbonded in a company aircraft that had been fueled with G100UL. GAMI says there are indications the unbonded sealant had nothing to do with the fuel, but because the tank was not inspected before the unleaded fuel was introduced there’s no way to prove whether the fuel was a factor. In its service advisory, Cirrus said the materials compatibility of the fuel is “inconclusive.”

GAMI also noted that the fuel has been used in other aircraft with the same sealant with no issues. “GAMI’s SR22 has had G100UL in the fuel tanks for most of the last 14 years. Recently, Cirrus engineers and management inspected the interior of those tanks, in person, using a borescope and found no evidence of any debonding by any of the factory applied sealant in that aircraft,” the company said in its statement.

GAMI is also disputing Cirrus’s claim that use of G100UL voids the warranties on engines supplied by Lycoming and Continental and used in its aircraft. The engine warranties both state that they will not cover damage from the use of “non-approved fuel” but GAMI noted the FAA has approved G100UL for all models of Lycoming and Continental gasoline engines. AVweb has contacted Lycoming and Continental for clarification on warranty coverage for engines using G100UL.

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. I’ve never heard of 100VLL so I looked it up at:

    It says that TOTAL avgas production is just 0.14% of total motor fuel produced (1.4 gal of avgas for every 1000 total gallons of fuel) at 180 million gallons in 2024. Blue 100LL has 0.56 g/L of TEL (half of the green version). 100VLL only reduces that down to 0.45 g/L. And for these tiny (relative) numbers we’re worried about PAFI / EAGLE. So every gallon of G100UL or equivalent only removes ~1/2 gram of lead/gallon. Figure how far your airplane can fly on one gallon; that’s that area you’re spewing 1/2 gram of lead on !!!

    Now I am bored with this whole lead thing.

    • Note that the spec, for TEL in 100LL is a range of 0.28 to 0.53 g/l.
      So, the ‘spewing’ could be 1/2 of the 1/2 gram.

      I’d be interested in knowing how little TEL could be used and still maintain the 100/130 octane rating ?
      I have been unable to find any info on this.!

      • BTW the min. spec is only in the Exxon spec for 100LL.
        None of the other suppliers list a min. amount of TEL.?

      • Jim, I’m not meaning to flame, but I’m confused about the actual number of the lead in fuel.
        I have read, and relied on, 0.015 gram per liter of fuel, and your number is way higher.
        How can we verify the actual number?

    • Hmmm, based on the contact with lead in handling, cleaning, spills, and operating an aircraft, I could appreciate that it would be nice to be rid of it forever. Sure we’re not carpeting the skies with clouds if lead, but cleaning the lead fouling on plugs not my favorite pastime. But I fully recognize I have significant cognitive issues, possibly from 70 years of kead exposure?

    • All agree lead exposure is bad.
      Airplanes use leaded gas.
      Airplanes are owned by “rich” people.
      Rich people get all the favors.

      Add activists,
      and you get the current situation.

      • Airplanes aren’t always owned by “rich” people as you suggest.
        Many flying clubs across the U.S. are full of very middle class pilots. Ours for example, has everything from wealthy to student pilots struggling to get their hours in.

        • In fact, most of us are poor BECAUSE we own an airplane!! I bet a lot of pilots will agree with me.

        • Aeronaut is correct on this. There’s no convincing the activist types that regular people fly little planes. Frankly, most of them are rarely bothered by facts. They aren’t usually that passionate about improving the causes they are involved in. Most of it is about their own needs and wants.

    • Your numbers are wrong by a factor of 3.7. The lead spec is grams of lead per LITER of avgas. There are 3.7 liters per gallon, so it’s really close to 2 grams of lead per gallon. I agree with your principle that it does not present very much of a danger to the environment.

      • Today when I was at the airport, I thought about what I wrote and realized I had mixed liters and gallons. Good catch.
        I wrote that early in the AM before my first cup of java so … I wasn’t yet coherent. 🙂 Still, it isn’t a lot when the airplane is moving around at high speed at high altitude. I see the deleterious effects on the engine as more important than the lead coming out of the exhaust pipe, however.

    • The issue isn’t about aircraft in cruise flight but rather the concentration of aircraft operating on, and around the airport. At many GA airports the ends of the runways and run-up areas are near the airport boundary with residential areas sometimes just over the fence. So when we do the run-up and full throttle, full rich, takeoff, prop wash pushes the leaded exhaust over the fence. It is these areas where lead is readily detectable in air and accumulates as particle fallout in the soil. It’s the kids in that trailer park next to the runway that the EPA is worried about. We need to stop messing around and get rid of leaded fuel before cities, that are desperate for open land to build new housing, use lead as an excuse to close down our GA airports.

      • It’s always about the “children,” isn’t it … did you say that with a quivering voice like that woman in the ASPCA commercial grifting for donations to save dogs?

      • The EPA isn’t worried about kids. Their record shows their real concerns and it’s not even the environment. It’s their own careers and politics first.
        Your last bit is the correct part though. The lead is a PR vulnerability. This is all about PR. This is just one of many reasons to continuously hammer home that the root cause of the continued use of lead is the FAA having suppressed innovation in light aircraft BY CHOICE for DECADES.
        I’m starting to wish I could hire a nun to come around and smack all you old farts’ knuckles for not getting with the program.
        Conveniently, it’s also the truth.

  2. I guess with all of these “Chem Trails” flying overhead the fear that your Cirrus is “spraying” those lead poisons up in the “cirrus levels” and it is raining down on our “children”. You have to use “buzz” words in a story or the “masses” won’t understand. You and your actual math, that will never be understood.

    • I’m more worried about “spewing” lead on the children. How does lead know to discriminate based on age and not affect anyone else?

      • The spewing is the same, but the result is different. Children’s minds are still developing, and lead can adversely affect that process.

        Adults are already as dumb as they’re going to get.

        • And, adults also fall for the same propaganda whether they’ve been exposed to lead or not.

  3. my new IO550 is still under it’s 2 year warranty. An email from Mr. Cateli Product Support Representative Continental Aero “The use of fuels that are not approved for your engine, will void your warranty”. Continental M-O Table 7-2 Authorized Fuels by Engine Model does not have G100UL listed.

    • Question is who decides what fuel is approved. FAA says G100UL is approved. I think Continental would have a hard time if it went to court, but I doubt they’ll ever get there.

      • Anyone can approve the use of a specific fuel. Airplane maker, engine maker, EPA, individual, FAA, etc. Some approvals mean more than other approvals.

  4. With any change in the status quo, there is going to some unexpected results. But fear of the unknown is no reason not to try. Until GAMI g100UL is in wide use, there will always be questions. We need real in service data. In God we trust, everyone else bring data.

  5. Cirrus should be promoting this fuel just like Rotax does because lead causes lots of engine damage, according to Rotax. It might reduce the cost to warranty their product.

    • Cirrus doesn’t make engines nor do they cover warranties for them. There are three distinct type certificates for every piston engine aircraft. The airframe (Cirrus) the Prop (Hartzell or maybe McCaully) and the engine, Continental. It is they (Continental) who hold that type certificate and it is they who determines what can be used in their engines to meet the specifications they originally provided when they obtained that type certificate. And, it is they who decide what is allowed under warranty and what is not. At this time, apparently there is nothing to gain by allowing the use of GAMI fuels for them. Just more risk. And, I wouldn’t be at all surprised they (the engine manufacturers) have a bit of a chip on their shoulders against the GAMI folks who literally made a business off an obvious shortcoming in their products. Installing a few appropriately sized injectors in each individual cylinder does not make you a fuel expert in my mind. IMHO

  6. For the sake of all that is holy; please give me unleaded 100LL.
    That’s all I need in my Grumman and it would be CHEAPER than even 100LL. Give us private pilots that at least.

  7. I started using UL91 in my IO-360 RV-8, and two years later my cat died, so I need to go back to 100LL. /s

    • Are you certain the cat passed due to UL91 infestation or possibly “Caticide”. Feline suicide rates are skyrocketing due to constant social media bullying and Facebook attacks. Those dern Dawgs never give up.

    • Yes. It has taken GAMI that long just to get to where they are, which is ridiculous. The FAA grudgingly approved the STC after all the testing that proved it is a valid replacement for 100LL.

  8. I have an Auto Gas STC on my PA28-151 and flew for years using gas from my local gas station. This was before they started “denaturing” the gas with alcohol. There were no side-effects besides a smooth-running engine and no bad mag-checks. I still have the jerry cans stowed in my garage. I can buy 100% gas at many stations, but now airports are restricting users from bringing in their own gas through various measures. Now I use Alcor TCP to mitigate engine lead poisoning and eliminate having to routinely clean plugs. Sure, TCP is a neurotoxin, but so is lead. But it is an added expense. If I could buy G100UL ANYWHERE within range of where I normally fly, I’d buy an STC right now. C’mon people, get off it and SELL ME SOME!

    • The airports try to restrict users bringing in their own gas cuz they lose revenue from the loss of 100LL (regardless of whatever other excuse they push). But they won’t dump the 100LL for UL94, G100, or MoGas (especially of the non-alcohol version). Let the airport/FBOs pound sand

      • They can “pound sand” until they go broke and close. As so many have over the years. It’s attitudes like that and pilots who don’t support those FBOs which is leading to so many of them disappearing. If you can’t afford to support them, maybe you should be looking for a different passtime.

  9. If an airport receives Federal funds, they cannot prevent you from fueling your own airplane. See FAA Order 5190.1A, page 4, paragraph e.

  10. There is never anything like a Political Narrative to skew results to something stupid and benigne! Anything to keep the status quo in power!!! Onward to the perfect world! Right…

  11. Cirrus’s Service Advisory looks to have been written by a committee comprised of a room full of marketing wonks and lawyers.

  12. Me thinks there will be many Cirrus sitting on the ground, fading in the California Sun. I’m not really sure how many other blue states are pushing for this nonsense. For those of you that you don’t know, Cirrus is a Chinese company. Perhaps a little politics playing here?

  13. 1. The FAA approval for G100UL applies to the engines, not necessarily the entire aircraft fuel system.

    2. Engine warranty coverage for G100UL use is unclear. While the FAA approves the fuel, individual engine manufacturers (Continental and Lycoming) have the final say on warranty coverage.

  14. Assuming there is no real environmental consequence to using leaded fuel in our aircraft, is there any concern that the supply of TEL will one day be gone? It is my understanding that there is only one company on the planet supplying TEL.

    • Only one company in the free world, and they’ve indicated in the past that they would continue to meet the demand. And if they didn’t, somebody else would – as long as there is a demand they will be a supplier.

  15. Let’s promote Jet-A burning re-cips. Like Delta Hawk, Diamond, and Steven Higgs Hawk V-4.

  16. Whether it’s PR, politics, the EPA, activists or any other perceived enemy, an unleaded world is inevitable. All the political inuendoes, snipes, and pissing and moaning in the world isn’t going to stop it. Like it or not, if your fiery chariot burns gasoline, it will eventually have to be lead-free.

  17. Good evening and two comments:

    1) Per Dave S…. I would be more concerned about the supply chain issue than the activists.
    2) The ubiquitous nature of digital content, access methods (aka smart phones), social media and ultimately what is considered AI has already undermined the cognitive abilities of our future generations more than leaded fuel or lead in general, more than any of us might realize.

    To caveat the last statement:
    1) This is my theory — needs proof.
    2) My perspective is from what I see as a teacher. Please note — I haven’t lost faith in the future generations….


  18. 100UL is inevitable given all the environmental regulation and pressures. The problem with UL94 or UL91 is that not all piston aircraft can use it (i.e., high compression engines). FBOs won’t spring for both 100UL and UL94/UL91 because of the cost of two separate sets of tanks/trucks and pumps. They’ll wait until there is sufficient demand for 100UL to offer it. They don’t want to buy a bunch of any fuel that they can’t sell. I bought the GAMI G100UL STC for my Lycoming O-360-C1F for $600 but my FBO doesn’t offer it yet and I can’t get it anywhere nearby. My engine is well out of warranty so that’s not the issue. It’s distribution and availability. I think Cirrus, Continental and Lycoming are all going to eventually approve 100UL fuel use but they are waiting for EAGLE to produce something useful since having ASTM certification is a golden ticket that lowers their liability. EAGLE is progressing at the rate of a wounded snail right now with 2030 as their timeline. Once we get to 2030 then the problem of distribution and availability will take another 10 years for EAGLE certified fuels.