Lycoming Clarifies G100UL Warranty Impact


The world’s largest piston aircraft engine manufacturer has confirmed it may not honor warranty claims on engines that have been run on GAMI G100UL unleaded fuel. In a statement to AVweb, Lycoming said that G100UL is not on its list of approved fuels and while warranty claims are assessed individually, the warranty “does not cover damage caused by operation outside of Lycoming’s published specifications or the use of non-approved fuels or lubricants.”

The full statement is copied below. The company did not say what is required to make that list but it includes leaded and unleaded aviation fuels and some unleaded automotive fuels. Its highest performance engines are generally restricted to 100LL in North America.

Lycoming was responding to a legal opinion offered by an AVweb reader who is a lawyer and high-performance single owner who disputes that claim. He said that since G100UL is approved by the FAA through an STC, engine manufacturers can’t reject warranty claims based on use of the fuel. Lycoming’s full unedited statement follows.

WILLIAMSPORT, PA – Lycoming Engines provides a Limited Warranty against defects in material or workmanship. Lycoming’s Limited Warranty does not cover damage caused by operation outside of Lycoming’s published specifications or the use of non-approved fuels or lubricants.

Lycoming publishes specifications for approved fuels in Service Instruction 1070. G100UL is not listed as an approved fuel in Service Instruction 1070.

Lycoming evaluates warranty claims on a case-by-case bases in accordance with the terms of its Limited Warranty. However, customers should be aware that use of fuels not approved in Service Instruction 1070 would constitute operation outside of Lycoming’s published specifications.

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. There it is. Pretty simple stuff. Owners operating with non- listed fuels ane lubricants are on their own and subject to the mercy of Lyco in having their limited warranty honored. The rest will be settled in court upon a conflict, or whenever the fuel manufacturer does the legwork to get on the holy list. Opinion remains generically irrelevant…

    • I wonder how the Magnuson-Moss Warranty Act would apply here.
      Before that law as passed in 1975 car dealerships would routinely deny warranty coverage if an owner didn’t get all their service done at the dealer, using dealer parts and oil. Even if the failure couldn’t be traced to the use of non-dealer parts and fluids.

      It sounds like Lycoming (and Cirrus, and…) are trying to do the same thing, in effect saying “it doesn’t matter who approves it – if WE don’t like it, you can’t use it.” This may run afoul of federal law.

      • Say some clever business guy comes along, develops a 0W-20 synthetic oil, and gets a government agency to approve the use of that oil in an engine designed for 5W-20. That businessman even has a piece of paper from that government agency that says it’s ok to use it in that engine. But no one consulted with the engine OEM about what they thought about it, and now they might have to fix all the problems associated with it. It’s not like Lycoming is demanding people use their 5W-20 branded oil. They just want you to use an oil that meets the 5W-20 specification. These new fuels are chemically different than 100LL. They don’t meet the 100LL specification for which the engine was designed. That’s all Lycoming has to argue in court.

  2. Lawyer costs to challenge a warranty denial would probably exceed the cost of a new engine.

    I expect there might eventually be a class action or federal suit if Lyco and other engine manufacturers don’t allow unleaded fuels.

    • Well, Lycoming and Continental may very well embrace and endorse unleaded av fuels —
      And most likely will — by 2030–
      However, Just not — GAMI juice , non ASTM’d.

  3. And according to AvWeb ,Swift Fuels is also seeking an ASTM spec for its fuel but is pursuing a supplemental type certificate instead of fleet authorization.

    • You didn’t mention what swift fuel you were referring to. UL94 marketed by swift is a fully ASTM spec Avgas that is approved by the manufacturers for many of their engines.

  4. It’s all fun and games and politics until 2030 rolls around and the entire US fleet is grounded. That’s only 5.5 years away folks. And if you think the environmentalists are going to cave, I have a bridge in Brooklyn for sale. These politicians better stop squabbling and start helping get an automotive fuel approved or this could be end of GA as we know it.

    • 2030, 5.5 years.
      Unless the world’s single source of TEL, Innospec, stops producing it first.

    • Not trying to start a fight here but why do we let environmentalists run the country? Write your congressfolk and vote!

      • Feel free to send any opinion to your rep in Congress on any topic, but vote? For who, and why? Voting is always the right thing to do, but do you vote for someone who hangs their hat on being anti-environment, very risky to try to get into or stay in office? Is fuels the only reason you would vote for someone?

        • You go vote. Then, you only vote for new candidates who you think sound promising until you are happy with government. If you are happy with the way an institution is performing, then, and only then, vote for the incumbent.

          It’s an easy strategy that avoids a lot of nonsense and if more people adopted it, then gerrymandering and a lot of other BS they pull would start failing to save them in their jobs.

      • Assuming lead in aviation fuel actually is phased out in 2030 and Congress doesn’t intercede, it will have taken 30 years from the time that happened for vehicles. It took more than 10 years of petitioning the EPA to get an endangerment finding. Neither of those timeframes suggest environmentalists are running the country. Instead, they seem reflective of a shift in public opinion over time.

        • Hard to place any blame. Aircraft certification regulations are probably the biggest hurdle.
          Without a defined high octane unleaded fuel how do lycoming and continental design the engine to run on an unknown fuel?

    • Not the entire US fleet. “Only” up to about 40% of it. The rest of us don’t actually need lead in our fuel and many of us are better off (per manufacturer recommendation) without it. But, for that 40%, the engine manufacturers have been sleeping on the job for 40-50 years and I’d be pretty mad about that if I were an owner.

      • The rest of you will then soon find yourselves in some rural airports waiting for the next shoe to drop while your cost increases even more and more manufacturers just stop trying.

      • Well worded! The airframe and engine manufacturers are not making the changes!! We need lower compression engines with the same horsepower, and they are doing nothing!!

  5. So this is what I find interesting: Whatever new fuels come (be they by STC or by new ATSM specification) there needs to be a process for being added to the list in SL 1070, and whatever similar list exists at Continental. As the article said, there probably isn’t a defined process for adding a fuel to the list since the industry hasn’t produced a new fuel in decades.

    Now, it’s a two-step process for new fuel suppliers. Step one; get your fuel approved somehow by a regulator. Step two; get that approved fuel added to the approved-fuels list of every engine manufacturer and every airframe manufacturer. Good luck with that.

    Just getting an ATSM-spec fuel only satisfies step one.

  6. I read the legal opinion and it does seem that this statement from Lycoming is not sufficient legally-speaking should it be challenged in court by an owner who had used G100UL and submitted warranty claims. The warranty terms aren’t specific enough when describing the meaning of “approved fuel,” and a statement after the fact isn’t legally binding. However, as another reader pointed out, the legal fees to pursue any such denial would likely dwarf the cost of an engine replacement.

    • I understand the presented legal argument that “approved fuel” is not defined within the warranty terms. However, Lycoming does have a separate document specifically addressing approved fuels for each and every engine. It is not unreasonable to connect the dots from the warranty terms to Lycoming’s SI 1070. If Lycoming did not have a published list of approved fuels, then the legal argument would hold more weight. Furthermore, what obligation does an owner/operator have to comply with the manufacturer’s Service Instructions? I expect there are other Service Instructions that, if not complied with, could compromise warranty claims.

    • The games around the word approved are only some of the games. The other problem Lycoming will run into is that they have to show a reasonable connection between the claim they want to deny and the use of the fuel. Good luck.
      They can’t simply terminate their obligations because you used the fuel. If you ask me, the only thing they might even try is using this to avoid liability in an accident case.
      Otherwise, this is some sort of political nonsense being played by Textron who owns both lyco and Cessna and is a defense contractor dependent on charity contracts that the DoD gives them occasionally to keep them as a viable vendor. (Consolidation has led to too few contractors necessitating this strategy for the DoD).

  7. These are two separate things. Installing or using STC-ed items is legal but whether something is covered under “warranty” has nothing to do with the legality of it.

    As discouraging as it sounds, I don’t believe there are any regulations with regard to what a manufacturer is responsible for to cover under warranty.

    This is no different, than say, you install vortex generators on a new airplane out of the factory via a STC and then claim the adhesive caused damage to the exterior paint. It’s very unlikely the warranty would cover that.

    • Bingo! Sierra Alpha.

      In fact Continental denies any and all warranty claims if the engine is modified in any way. Put an engine STC like a turbo or FAT supercharger kit and no warranty. Continental told me in writing any engine STC immediately voids warranty.

      • Quite true, ND. But the problem is that the STC to use G100UL does not modify the engine in any way. By extensive testing, GAMI has demonstrated that its fuel is totally mixable with 100LL in any concentration of either product without causing any issues for the engine. No adjustments are needed, so the change is totally transparent to the engine. What I find interesting is that Lycoming lists Swift 94UL as an acceptable fuel even though they now maintain that it contains aromatic compounds that can damage the valves and valve seats in their engines. Oops!

  8. The engine manufacturers saw a way to avoid liability and are jumping on it. It’s about the money because that’s all it’s ever about.

    George’s mistakes were thinking that a safe unleaded fuel was the goal and not endless government R&D money to chase failure, then not involving enough politicians in his project.

    Cui bono?

    • Right. And the juice to push against the petrochemical industry.

      The ATSM standard is deeply embedded for miles in decades long contracts throughout the supply chain. Frequently these contracts were signed years ago and addendums are added to adjust terms like volume pricing and additional products.

  9. So Lycoming is ok with UL 94, the one that was thought to cause valve seat recession, but not G100UL?? (see SI 1070)

  10. It kind of begs the question of whether Lycoming intends to honor warranty claims for all those UND engines. 94UL is a factory approved fuel for those engines.

  11. I am not a lawyer. But I am a Lycoming customer. Not just a “User”, but a customer who purchases very expensive Lycoming parts. In some quarters, the customer is always right. Then there is Lycoming. As customers, Lycoming takes us for granted and is less interested in our thoughts and needs than is the FAA. And the cruel fact is there is very little we can do about it since a very high percentage of Lycomings sales are directed by airframe certifications.

    GAMI has a product that involves a confidential formulation – a very successful “recipe” if you will. This product has existed and been tested in aircraft in flight since 2010. GAMI has issued Press Releases showing a number of famous air show performers like Patty Wagstaff who have been running their aircraft on G100UL. AOPA is drawing close to 200 FH in their Beech Baron with one engine running 100LL exclusively and the other engine running G100UL exclusively. Mike Busch has agreed to monitor that aircraft for any fuel related problems and specifically for any occurrence of valve seat recession. Embry-Riddle University Flight School tested G100UL without a single problem. And the list goes on.

    But any confidential formulation needs protection before you can share specific data based upon that formulation. If you are thinking “patent”, that only works after the fact – after damage is done. The best method of protection is through a “Non-Disclosure Agreement” (NDA).

    GAMI’s NDA has been offered to several businesses and persons including both Continental and Lycoming. Rumor has it that Continental signed the NDA and returned it to GAMI. Lycoming refused. Now if this is true, what are we as Lycoming customers supposed to think?

    AirVenture is just around the corner. Perhaps if enough “customers” confront Lycoming in Oshkosh for their explanation on all these matters, some people in Williamsport might wake up! If we are going to get Lycoming to start respecting us, we need to confront them.

    • Lycoming is a bit player in all this. Big oil and the politicians they support are the drivers. This is America where one dollar equals one vote. Who has the dollars? Not Lycoming and certainly not us. Lycoming, the GA alphabet groups, the FAA….are all subject to the pressure exerted by big corporations and their puppet politicians. That is what we are witnessing.

      • One dollar, one vote? So in your universe, Trump was never president?
        Big Oil? Who is “Big Oil” and why do they care so much, and how come they keep letting the Democrats win offices again?
        Finally, how many divisions do these corporations have? Why haven’t they taken over Canada? …wait, did they take over Canada?

    • I would not like to be a Lycoming sales rep at Oshkosh this year. They might have to answer some pretty tough questions from frustrated owners and prospective customers. With many consumer products, if you don’t like one company, you can switch to a competitor’s product. Our problem, as aircraft owners, is that you don’t have that choice. If I get mad at Lycoming, I can’t pull my engine at overhaul and drop in a Continental or other competing engine. And they know it. They don’t have to treat existing customers with any respect simply because they have your business so long as you own that airplane. And, very few of us can afford to buy a brand new airplane with a competitor’s engine.

      • At this point, I’d not buy anything with a Lycoming or Continental again already. Why do I need a four seat plane anymore? Maybe this uncertainty will add to the list of folks in my camp.

  12. Sierra Alpha has hit the nail squarely on the head. An STC only says that you are not busting the regs if you put it in your plane. Has nothing to do with consumer protection. Also, be aware that ALL documentation (including Service Instructions) provided by the manufacturer about proper use of the engine at the time of purchase is pertinent to the warranty agreement. Not being an approved fuel according to the engine manufacturer is not something they just came up with now.

    In addition, if the big guys are in control of the process, why didn’t they approve their own fuel willy-nilly? Seems counter-intuitive. Maybe the 90% membership approval (all stake holders, not just manufacturers) has something to do with it? Personally, I say take every minute of the 2030 dead-line available and develop as many strong candidates as possible and thoroughly vet each of them – out in the open.

  13. This is not specific to Lycoming or any other engine manufacturer. There is an “approved list”. Getting on that, likely costs a lot of mula. Same issue with a certain German car manufacturer. Example: Oil meets the specs, payment rendered, “meets LL04 standards” is allowed to be printed on the bottle. Put it in your motor and the warranty stays intact. Put a higher spec, better performing racing oil in the motor that far exceeds all specs issued and find yourself up sh..creek when that stupid engine goes poof. They will actually laugh at the customer.

    Cars stop on the side of the road. Planes not so often. People get hurt, die or even worse: lawsuits are filed! Everyone with a pulse is culpable or somehow involved.

    Whoever is in charge of getting on that approved list, has a steep homework assignment ahead. Maybe someone else paid more to be exclusively listed. Everything has a price in our industry. Everything.

  14. So, everyone ends up in court after trying to adapt a fuel to a design application for which it was never intended.
    Air-cooled, large-bore, lightweight, predictable, reliable. Which of these design attributes are you willing to give up to make unleaded fuel workable?

  15. Why has no one posted the airframe and the engine warranty information from their GAMI STC’s? It doesn’t seem that great (if T&C 15 and 16 applies to the STC) if everyone is clinging on to the OEM to bail them out if the damage is related to the STC they chose to install. Going the STC route also means being tethered to any FAA AD’s or EAD’s.

  16. It seems to me that engine warranties are 1) short; and 2) limited. I have an airplane with a Lycoming O-360 engine and it is long out of warranty, and about midway through the TBO. No matter what fuel I put in it, it will not affect the warranty. Performance perhaps, but no warranty problem. I am disappointed that every time I have my airplane’s annual inspection performed, the fine wire spark plugs are fouled with lead. Often the first sign of lead fouling has been a slightly rough running engine. I have tried leaning out the mixture to see if that affects the lead fouling and the answer is “not much.” As soon as UL avgas is easily available, I plan to use it (assuming I have not retired from flying by then). The environmental issues, from this aircraft owner’s standpoint, are incidental (positive to be sure, but incidental).

  17. All engine manufactures will have an approved item/fluid list for their own engine. That is all based on their testing and what they feel is the best for their individual engines. Just like car manufactures, some allow e85 and others don’t. So the FAA, which doesn’t manufacture engines, can approve a fuel for sale to the aviation industry, because they have tested it and it has met their legal liability thresholds. They have no say in what the engine manufactures will or won’t approve for their engines. It’s like when you were a kid and your excuse for doing something that your parents didn’t want you to do….”but jimmys parents said it was ok”…we all know how that turned out. Haha

  18. Since another unleaded fuel producer has dropped out of the FAA/astm testing, I get the feeling the oil company avgas producers are waiting for the EPA to ban 100LL so they can get out of the avgas production all together. Since avgas sales are such a small quantity of their business with a huge liability exposure, I think those avgas producers could care less about continued production, or pricing. Which would result in grounding anything that can’t run on ethanol mixed auto gas, or the cost increasing to the point of costing as much to operate as a turbine powered plane.

    • I am not that far along, but I’ve always felt the Avgas departments of these producers are pretty much a rounding error and it’s not something the Board or the C suite really gets concerned about.