GAMI Unleaded G100UL Eyed To Go On Sale In California By Summer


Aircraft operators in California will likely be the first to be able to fill their tanks with unleaded 100 octane aviation fuel. General Aviation Modifications Inc. head of engineering George Braly told AVweb the company has signed a licensing agreement with petroleum company Vitol Aviation and that company is now in the process of producing the first large-scale batches of G100UL® avgas. At this time, the expectation is that G100UL avgas will be available to the West Coast in the first half of this year. “The initial deployment will be in California,” said Braly. Vitol is now reconfiguring refining, blending, and storage facilities in the Gulf Coast area to produce the fuel and has obtained the necessary authorizations from the FAA to make and sell it. Braly said it’s still not clear which airports will inaugurate the sale of G100UL, but several airports have banned the sale of leaded aviation fuel and those who need the higher octane have to fill up elsewhere.

In September of 2022, GAMI obtained a blanket supplementary type certificate (STC with Approved Model List) that allows the use of G100UL in every gasoline engine used in certified aircraft in the U.S. To use the fuel, aircraft owners have to buy the STC for their aircraft, which Braly says is a simple one-time online form for each aircraft. The cost is based on the horsepower of the engine in the plane. The fuel will also cost more than 100LL. “The premium components required to make this fuel cost more,” he said. “There’s no such thing as a free lunch.” The costs of the components in a gallon of G100UL avgas is between 85 cents and $1.15 per gallon more than the cost of those components used in making a gallon of 100LL. That difference depends on fluctuating market prices for the ingredients. How much those costs will translate into the ultimate pump price will be up to the various wholesalers, distributors and FBO retailers in the supply chain.

Braly said the ultimate goal is to make the fuel available everywhere as the industry transitions out of the use of leaded fuel in compliance with federal regulations that are expected to ban its use in the next decade. G100UL is not formally in or part of the FAA/aviation industry’s Eliminate Aviation Gasoline Lead Emissions (EAGLE), as GAMI had already obtained its initial AML STC before that program was created in early 2022. However, G100UL avgas remains the only visible high-octane replacement for 100LL that has so far been approved for use. Swift Fuels has an unleaded 100 octane fuel under development as does a partnership between Lyondell, a chemical company, and VP Racing, which makes fuels for racing engines. Phillips Petroleum and chemical company Afton have paused the evaluation of their fuel in the EAGLE program because it failed a key test in the evaluation process. EAGLE has set 2030 to have a universal replacement for 100LL “without adversely impacting the safe and efficient operation of the existing fleet.”

GAMI has been working with AOPA to demonstrate the fuel by running one of the engines on AOPA’s Beech Baron on G100UL and the other on 100LL. The dual-fuel Baron started with freshly overhauled engines and has now flown over a hundred hours in that configuration and will take part in the AOPA Fly-in at the Buckeye Air Fair at Buckeye Airport in Arizona from Feb. 16-18. Braly said AOPA President Mark Baker has played a key role in getting the fuel into the public eye with the Baron demonstration and participation in the airshow.

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.


    • The first paragraph is the news, the rest is just a rundown of the history of GAMI’s fuel for anyone not aware. That’s a fairly standard way of writing an article on a basic story like this.

      • Last November (2023) UND flight school halted use of Swift Fuel 94 UL because of accerated valve wear across their fleet of training aircraft.

        What’s the potential for GAMI to have the same adverse effect??? UND reported returning to 100LL as the only approved fuel for their fleet. Where is the discussion of the UND study and results as we explore other UL options???

        • As of right now, valve measurements on the AOPA Baron running GAMI’s G100UL on one engine and 100LL on the other show no accelerated valve or seat wear. There are lots of questions surrounding UND’s methods and results, which to my mind makes their conclussions ambiguous.

  1. Very surprised that there is not a lot of protesting of the increase cost of the new UL100 products that will make fuel so expensive that it probably will end aviation as we know it, even though 70% of the aircraft could run on the current fuel if the lead was just removed. The rest of the aircraft could quickly be modified as we found out when 115/145 leaded avgas was no longer available. The 100 octane group that calls this the only answer is just holding the 70% group that can use the alternative, hostage. At a point maybe starting in California when lead is no longer legal to be added to any Fuel, the Aviation community will finally be forced into making real decisions instead of what they’ve been doing for the last 30 years. Which works out to basically nothing but a lot of noise.

    • I for one would certainly not welcome a $1/gal increase to use the GAMi fuel. Mine will run just fine on Swift 94UL but until they get the price down somewhere near 100LL I will continue to use 100LL. It’s a catch 22, no one will use the UL fuel due to the cost, yet until the volumes go up the cost will not come down.

    • No one in the 70% is being held hostage. Swift 94UL has been available for years yet the demand isn’t there. The reason for this is probably because these 70% of the aircraft engines are in the minority when it comes to the volume of fuel they consume. Why aren’t the 70% of the operators with these engines fighting to secure the more expensive 94UL which is essentially 100LL without the lead?

      As far as I know, there are no existing modifications that can quickly be made to the 30% of the engines that burn the majority of the fuel and presently require 100LL, like my IO-550. If you know of any ready and quick modifications that will allow my engine to produce it’s rated power and not self destruct in minutes with 94UL, then please do share. The death of aviation as we know it would be the elimination of the majority of the demand for any aviation grade fuel. That would most certainly result in higher costs as producers drop out and supplies diminish.

      • Of course, there are no readily available modifications. Why would there be as long as everybody can get 100 LL. Currently there would be no reason to make modification kits for aircraft engines. When they outlaw lead or set a drop dead date to end lead in aviation fuel, the modifications will come quickly as there would be a demand, just like you already pointed out about 94 UL.

        • The drop dead date has been set. The EPA has published the endangerment finding. Something is going to change and it’s coming really soon as compared the the historical pace of these matters.

          G100UL exists, it is going to hit the market. The market will decide whether or not it has legs.

          I would not hold your breath for any “kits” to retrofit existing engine designs. The issue with these high performance engines is detonation, not wear. Either the fuel is engineered to not cause detonation at the high power settings, or the engines need to be derated to reduce power output.

          The latter is the way it is done in the automotive world with the modern sensors and controls that can monitor and alter engine performance several times per second.

          That simply does not make sense in aviation where you cannot have an engine management system reduce power by a significant percentage during takeoff.

          Derating is also not an option because many designs would not be capable of doing anything useful.

          Changing the engines in any of the ways noted above would all require recertification of the types, etc. The costs to perform such testing across all types of airframes would be extreme.

          I have flew behind a diesel engine aircraft for years. It was an SMA powered 182Q done under an STC. I have nothing wrong with entertaining such changes, and it was fun to fly, but we’re talking about a conversion that was around $100K parts and labor in 2007 dollars and had many quirks. How many owners are prepared to pay over $100K? That is a realistic number to chew on to consider what it might cost to adopt clean sheet designs. Then one must also consider how many types would get STCs for such things? Will it fit under the same cowling (probably not), how many types are still flying and therefore is it worth the effort to certify? etc.

          If there is a “kit” that can stop an engine like an IO-550 from detonating with an unleaded aviation grade fuel (presently 94UL is the only game in town) then please let me know as I’d love to see what you have in mind. What sort of changes are you thinking are needed to make this happen?

          • The research is already been done. They know that normally aspirated engines can run on lower octane fuel by using water injection. In fact, it was discovered that the water injection actually increased the horsepower for takeoff when it was used when compared to using higher octane fuel and no water injection. Water injection system have already been developed for the Cirrus aircraft to allow it to use 94UL. I have also contacted ram conversions, and they said that using improved efficiency, intercoolers they have installed can eliminate the need for a higher octane fuel and preserve full rated power. There is also an intercooler conversion kit for a pressurized Navajo, and an inner cooler kit for a turbo charged 210 that would also allow the use of UL 94.

      • The “cheap” easy way would not be a kit but would require an STC. There are 3 basic ways to reduce detonation: reduce compression (expensive parts), improve combustion chamber shape (expensive parts), reduce boost (not so expensive) and puling back a few degrees of ignition timing. On NA (normally aspirated) engines this may be all that is needed for them to be happy running 94UL or even auto fuel. The IO-550 only runs 8.5:1 compression which is very low. Yes some power would probably be lost but would it be more than is lost with a 1000’ increase in density altitude? The aircraft would be in service with the available fuel. How much if at all the performance would really be affected we won’t know till someone does it. Turbo’s are a bit harder but essentially the same strategy, lower timing then pull boost. Might have to run turbo normalized at 300hp rather than boosted to 360hp as a stop gap till the next overhaul. Essentially your “kit” would be mags or electronic ignitions with reduced timing advance for NA engines and the ignition plus reduced boost controllers for the turbo engines. Runway length would be increased, a very small percent of the fleet would have to seriously consider impacts to performance and operation, BUT they could also just run G100UL or whatever VP comes up with.

        • Any reduction in power would nullify what little single engine climb performance most light piston twins have making their use for charters illegal. Those are a large part that 70% of 100LL avgas fuel consumption. On single engine planes it would greatly reduce the go around performance requiring reduced weights or flap use requiring additional landing distances. Who would pay for recertification for most of those issues?

    • If that 70% of small airplanes that can run on 94UL consumed enough fuel, the old 80 (red) octane would still be sold. The planes that were modified when 115/145 was phased out were transport category planes with radial engines. Those engines/planes had a lot more certification margin than normal category small airplanes. Most of those radial powered planes had to use reduced power settings and lower takeoff weights to meet certification standards. Most light airplanes are already at minimum certification standards for performance and would not be able to meet those standards with reduced power running on 94UL or auto gas. If cost effective modifications were available, most owners would have already modified their engines to accommodate the lower octane fuels.

      • No owners of engines that need 100 octane fuel would modify them at this point in time there is no incentive so what you’re saying is ridiculous.

    • Makes you wonder if the Government is demanding higher priced fuels to do just that; force the small fish out of the skies to make way for more “passenger aircraft” as they like to call it. It’s almost brilliant to ban small GA under the guise of health and safety.

    • “The rest of the aircraft could quickly be modified …”
      Most of those aircraft are working birds; tell us how to modify them, so that you still have the required takeoff power at gross?

  2. I’m in northern California, and I’d consider using 50-50 , G100UL and 100LL to reduce the lead that gets into the oil, as long as the cost is $1 or less than 100LL.
    I’ve had 3 stuck exhaust valves in the last 2 years, which I think is due to our low oil use of 9-10 hrs per qt. The oil analysis shows lead levels of 3,000 ppm..!!
    It’s a long process to ream the guide and get the valve back in.

  3. We can’t get rid of lead fast enough. Every time we hear about a $1 per gallon increase, everyone predicts the end of aviation. I remember when avgas was less than $1/gallon, and everyone said they’d quit flying if it hit $2/gallon. We’re still buying it at $8/gallon.

  4. Sorry, i’m not buying into this. Too fast, too soon. The military uses 10x as much fuel as general aviation. Probably more. Are they going to use lower octane? Of course not, but a bunch of money hungry investors are willing to let many small A/C pilots/operators pay more money, shorten the life of our pistion engines, and risk failures costing someones life?

    Its not a question of if, it is a question of when. What is the shelf life of this new fuel, when it sits in tanks for a couple years, including hot-cold weather transistions.

    When folks put their own fuel in at night, from unattended FBO’s whats to insure the wrong fuel is not put in, or worse- for you California types, when 100LL is not available, and a tired pilot just wants to get ‘home’ with his family. Do expect me to believe they are going to sleep in the airplane, until morning light?

    My A/C investment is near the cost of a house. I will sell, and many will. EPA is not our friend, and everyone knows this. Ethanol gas in cars is a net sum loser, period, but hey, the law makers forced it down our throats, literally, for our fuel injection systems.

    Non stop wars fill the skies of entire cities, every day. Do not kid yourselves, a lot of bad chemicals. Wars will never end. So EPA, what say you?

    When the small A/C market shrinks to below survival rates, and young kids no longer have the opportunities to fly that we once did, you (EPA) can pat yourselves on the back, and choke on your fancy retirements and other incomes.

    -Stephen G. owner/pilot for 16 years.

    • The only thing that the US military really cares about with 100LL is getting rid of its usage of it. The only two military aircraft that I’m aware of that still use 100LL are the T-53A, which are 25 Cirrus SR20s used by the Air Force Academy, and the RQ-7 Shadow drone used by the Army. The rest use JP-8. I know that the Army has been looking at a diesel replacement engine for its RQ-7 fleet for some time and it wouldn’t surprise me if the Air Force Academy did the same thing with the T-53.

  5. Water/methanol injection shaves 13 octane point off an engine without any loss of power. IO-520’s have been approved for it since 1986 in Barons and 210’s. But don’t take my word for it, look it up on the FAA website: STC SE2197CE.

    • How much does that system cost to install, is it available for other aircraft requiring 100-octane, and how much does the methanol cost?

    • The FAA’s website doesn’t show the details, only this “Add the following approved fuel: leaded & unleaded automotive gasoline 91 minimum antiknock index (RON+MON)/2. Intermixing with aviation gasoline also approved.”

      If it’s water and methanol, how much do you have to carry, and where are you going to put it? Does your airport carry methanol? What about the other airports you travel to?

  6. This may be a dumb question, but what will be the status of light aircraft that are approved for 80/87, and/or those that have been previously approved for unleaded mogas under one of the auto gas STCs (EAA or Peterson)? Even though I still use straight 100LL in my Champ (powered by a C85-8), in nearly 37 years, and well over 2000 hours I’ve never had a problem with stuck valves or lead fouling–problems I’ve heard many others complain about over the years. Nevertheless, I’d be happy to switch to G100UL at some point if it ever became locally available and made sense to do so, but I’m not sure I want to pay NBAA for yet another paper STC just to obtain the privilege.

  7. I should purchase an STC to replace 100LL which my aircraft was never certified nor STC’d to burn in the first place? I think NOT!

    100LL was a “Compromise” put forth by the fuel distributors to go eliminate the costs associated with stocking and maintaining fuel farms for 2 different grades of Piston Engine fuel types……Namely 80 Octane and 130 Octane. It’s AMAZING how many people don’t look at HISTORY.

    My 7:1 Compression Engine (which makes over 200HP) was designed and certified to run on 80 Octane “and above”.

    If the Aviation Community / AOPA/ EAA and the FAA want to boost flying activity and fuel sales, GA airports would do well to stock and already approved fuel (MOGAS) which can service over 70% of the fleet. At a reasonable price.

    For those who insist on or need High Compression Engines, let them purchase the new fuel. Sell it at the major airports or those airports which cater to the 30% of the fleet running high performance aircraft. 

    I have no problem finding MOGAS. Routinely making trips from Florida to the UP in Michigan and not buying a single gallon of 100LL.

    • Of course, the biggest problem with MOGAS is trying to find it without the damaging ethanol. There is also the concerned of the higher vapor pressure of auto gas that is sold in the winter months that can cause vapor lock and boil off of the fuel at higher altitudes. If those problems can be resolved, I think this might be a very good solution.

  8. What would the next steps be beyond the GAMI STC? Could this fuel be approved to the same status as 100LL where no STC is needed? If so, how?

    • NO.
      What would the next steps be beyond the GAMI STC? Could this fuel be approved to the same status as 100LL where no STC is needed? If so, how?
      NO- Because the STC approach to ‘certification’ was how the FAA and Braly GAMI bought into the entire approval process under the AML GAMI program offering.

  9. Can’t believe this has taken so long. I have had the STC sitting on my desk for a year waiting to be applied (i.e., attaching the stickers), but I’ve held off because the fuel wasn’t here.

  10. Stupid me! When I read the article Headline “GAMI Unleaded G100UL Eyed To Go On Sale In California By Summer”, I thought that “Go On Sale” meant that it was going to be cheaper than 100LL! Perhaps a better Headline would have been “GAMI Unleaded G100UL Eyed To “BE SOLD” In California By Summer. Haha!😂

      • See Paul Bertorelli’s AVWEB article from 9 Nov 2023 titled: Citing Valve Damage, UND Drops Unleaded Fuel And Returns To 100LL (Updated)

        Paul said the findings were based on school aircraft use summed to well over 40,000 hours… which would provide very solid stats.

        Paul also mentioned that similar adverse effects were found in the 70’s when auto engines designed for lead amended fuel were summarily switched to UL mogas. Swapging a car engine is pretty cheap… less than 10% of swapping aircraft engines. Ditto for the valve guides.

    • Does ‘on sale’ include additional expense to correct the valve wear resulting from at least one of the constellation on UL manufacturer’s formulation? UND DROPPED the UL fuel it was testing after just a few months of monitors its fleet found unacceptable accelerated wear of valve guides fleetwide attributed to the UL fuel. What’s the cost of a set of valve guides every 500 hrs or less on a 2000 hr TBO engine?

  11. With the media output the last few years about fossil fuels,i can’t help but wonder if 100 low lead users aren’t being singled out as the weak spot,to be brought down in full view of other fossil fuel consumers

  12. Join us for A VIRTUAL cup of coffee, a donut, and a LIVE WEBINAR as Chris D’Acosta, Swift Fuels CEO, discusses current and future Swift Fuels plans for the safe transition to an unleaded fuel for piston aircraft. Chris will share what’s happening with their high-octane 100R unleaded avgas product and their premium UL94 unleaded avgas. He will also share tips, techniques and monitoring necessary to ensure safe operation of an engine using these fuels.

    To view further details and registration information for this webinar, click here.

    The sponsor for this seminar is: MN FAASTeam.

    Saturday, February 24, 2024 at 09:00 Central Standard Time (07:00 PST; 08:00 MST; 10:00 EST; 05:00 HST; 06:00 AKST; 08:00 Arizona; 15:00 GMT)

    • Please ask Mr D’Acosta to discuss the UBD findings when UL was tested on the UND fleet.

      Is a resulting research note available yet for their aborted foray into UL land?

      • The University of North Dakota Stopped UL94 Use Following Valve Recession Concerns, according to UND chief instructor Jeremy Roesler, and the school has switched the fleet back to unleaded fuel over the summer of 2023.

        UND boasts a robust flight training program, with the fleet of more than 120 aircraft logging more than 46,000 flight hours between June and October.

        “The aircraft were flown to POH procedures,” Roseler said. “The UL94 fuel was on spec.”
        When routine maintenance detected abnormal exhaust valve recession, Roesler said the decision was made to revert back to 100LL.
        While many flight schools across the country are making the transition to operations using 100LL aviation fuel to UL94, the University of North Dakota (UND) has reversed course. UND has returned to 100LL after citing an issue with “exhaust valve recession” in the Lycoming engines that power its fleet of Piper PA-28-181 Archers and PA-44-180 Seminoles.

        According to Richard Scarbrough, A&P mechanic and contributor to FLYING, “exhaust valve recession is when the valve sits too low in the seat.” If the valve is not properly seated, there can be “blow-by” that can result in an Un-commanded loss of engine power and compression and, in worst cases, valve failure.

        “Exhaust valve recession can result in valve discoloration—first red, green, then purple. It can also erode the guide,” said Scarbrough, adding that at this time no one has attributed exhaust valve recession to a lack of lead in the fuel.

        According to an article on AVweb by Paul Bertorelli, UND set up a maintenance monitoring program to track any potential challenges with the use of UL94 prior to making the switch. To monitor for cylinder wear, the school conducted regular compression checks on its fleet of Archers and inspected the clearance between the rocker arm and valve stem. If the valve seat is recessing, this clearance will progressively diminish as the valve recedes farther into the cylinder head. If the recession becomes deep enough, the valve won’t close properly against the seat, and power loss or burned valves can result.

        UND director of maintenance Dan Kasowski said the Lycoming-specified minimum clearance is 0.028 inch, and some of the cylinders exceeded this limit.

        According to Roesler, when the school started to find issues, it decided to switch back to 100LL.

  13. Checking the Braly website, their STC pricing for my aircraft will be $190 for the STC ( 100hp ) and with the minimum additional pricing per gallon above and beyond 100LL pr gallon pricing as stated by Braly himself; will in my area bring the cost of a gallon of Braly GAMI fuel to $8.11 per gallon. And that is without further FBO add on costs and local taxes, etc… etc..
    I just returned from SOCAL as my daughters reside there and the 2 FBO’s in that area of very small GA aircraft types both anticipated a $9.00 per gallon Braly GAMI 100UL fuel once all is said and done.

    • Here in Northern California 100LL is now $5.05 to $5.99, so if G100UL is $1 more, that puts it back to $6-$7 per gal., like we had last Summer.

  14. Once again, the blanket statement about STC being required, without any information for the 10+ percent of the piston fleet who fly E-AB aircraft for which STCs do not (can not) apply. Please include that info whatever it may be!

    • Known as G100UL, the fuel was initially approved in July 2021 for a limited number of engines, including Lycoming O-320, O-360, and IO-360 piston engines. With the recent FAA nod, the Approved Model List now covers “every spark ignition piston engine and every airframe using a spark ignition piston engine in the FAA’s Type Certificate database.”
      The STC covers all spark ignition piston engines in the FAA’s Type Certificate Database “without exception,” according to Braly. The STC is 18 pages long and includes more than 1,800 engine makes and models.

    • “Is an experimental aircraft…. that has no type certificate…. required to purchase an STC?”

      D said : “I looked for my make, model, & engine type and found zilch …”

      S said: “Lots of experimental aircraft will be off the hook on this one…”

      “However, Braly through
      GAMI mentioned elsewhere that they’re helpfully coming up with a path for E-AB owners to purchase the STC, in case they’re unable to figure out how to produce a wing and engine placard sticker on their own.”

  15. schmookeeg said:

    “so your engines you exchange don’t have any other STC’s that are not transferable? …like GAMI fuel injectors? …or cooling baffles?

    Yeah… I’m a bit turned off by the STC being locked to engine serial number. That means this is a recurring charge (I do exchange engines over field OH) to get permission to buy the fuel that can’t be bought yet. What? I’ve bought some stupid-ish before, but that seems like an extra-frivolous torching of $1200.”