GAMI Awarded Long-Awaited STC For Unleaded 100-Octane Avgas


After more than three decades of research and development, general aviation finally has an approved unleaded 100-octane fuel. At AirVenture on Tuesday, the FAA formally awarded a supplemental type certificate (STC) to General Aviation Modifications Inc., the Ada, Oklahoma, company that itself spent more than a decade developing a fuel it calls G100. The fuel would be a drop-in replacement for 100LL which, despite lead content, continues to be manufactured under ongoing dispensation from the Environmental Protection Agency. But it may be quite some time before the fuel is fielded in volume and GAMI says it will probably cost 60 to 85 cents more than 100LL does now.

The STC comes after GAMI development work that started in 2009. It approves the use of G100 in just one type of aircraft, the Lycoming-equipped Cessna 172s. GAMI’s George Braly said that after some additional testing, the STC will be expanded to eventually cover the entire general aviation fleet, although the timing for that expansion remains unclear, as does how the fuel will be fielded in a market that continues to be driven by 100LL. GAMI says the expansion may occur in nine months to a year. Braly said GAMI has an agreement to distribute and manufacture G100 through Avfuel, a nationwide supplier that delivers about 40 percent of piston aircraft fuels to the U.S. market.

Volume manufacturing details remain to be worked out. Currently, 100LL is believed to be manufactured in about five U.S. refineries owned by Phillips, Chevron and Exxon. While Shell markets 100LL in the U.S., it no longer owns its own refineries to produce the fuel in the U.S. It does produce 100LL in Europe and it brands fuel it sells produced by other refiners. Chemically, G100 is a blended fuel consisting of a high-octane alkylate and a proprietary aromatic additive package that boosts the octane to a level equal to or higher than 100LL. As such, it can be produced in any refinery or facility capable of receiving the components by rail or by any refinery currently manufacturing 100LL.

Fielding of the fuel may turn on actions by the EPA or regulators in other countries where leaded avgas is still used. Lead as an additive or component in many products has been phased out since the early 1990s, but general aviation remains the primary source of airborne lead pollution, according to the EPA. When the automotive market converted to unleaded fuels, general aviation was given relief from that rulemaking because no other additive yielded the required 100-octane. Beginning more than a decade ago, the EPA focused on aviation lead emissions as a hazardous pollutant and after years of delays, it had intended to issue a so-called finding of endangerment in 2017, with potential rulemaking to eliminate lead entirely in 2018. However, according to the EPA, the Trump administration put those plans on hold and the agency has restarted the process. “The review is ongoing. We do not have additional timeline details to share at this time,” said an EPA spokesman.

Meanwhile, European regulations are examining rules to eliminate the production and importation of the tetraethyl lead that has proven unique in its ability to raise octane to required values. According to the FAA, a ban on TEL would eliminate the only remaining source of the additive in the EU, Innospec Inc., which manufactures it in the U.K. Innospec has said it would continue to produce TEL as long as there is demand for it. It’s not known how the U.K.’s Brexit withdrawal from the EU would affect this regulation, but the EU could still act on its own.

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  1. “GAMI says it will probably cost 60 to 85 cents more than 100LL does now.”

    Give me no alcohol UL93 no for 85 cents LESS than 100LL and I would be overjoyed! Paying more for 100UL over 100LL is dumb and costly and is yet another cost increase for GA.

    • As has been discussed many times over…

      An alcohol-free UL93 fuel would only cover 30% of fuel sales. Take the current market, set up a second set of pumps and deliveries to sell less then 1/3 of before would result in a higher, not lower price. Double your infrastructure costs but sell 70% less volume? There’s a winning combination.

      I don’t want to pay more in fuel, but splitting the market won’t make it cheaper. At least with unleaded gas we should enjoy reduced engine maintenance costs. Lead compounds foul plugs, contaminate oil, and corrode metals. Modern car engines wouldn’t perform nearly as well as they do if we were still using leaded fuel.

      • Alcohol & lead free fuel has been in use by many operators over many decades now. When I first started flying, I could find mogas at many airports at a reasonable price, either cheaper than 100LL or at the same price. I STC’d my a/c when I bought it @ 250 SFRM, and continue to run it to this day. I ran that engine primarily on mogas, to double TBO, twice. Aside from the engine basics: lead is bad for engines, lead is also bad for living things. I fly on the average 300 hrs per year, my home base does not carry unleaded fuel so I, and many others tanker it in. They used to carry it, but complained that they didn’t sell enough, so they dropped the tank when the new FBO came on board. The field had 100LL, Mogas, and Jet A when the new FBO took over. The first thing done was the price of fuel increased 25% across the board. The second thing done was mogas was dropped and the price of 100LL increased another 15% to be the third highest in the state where it remains to this day. My missions are 700 nm so I had justification for adding ER tanks and now tanker mogas. My second base does not have mogas either, but its 100LL is nearly half the price of my other base. Mogas is available 20 nm away at half of that price. The FBO owner is now complaining that he is not making enough on 100LL because the JetA volume is so much higher that it’s not worth it to pump it to him. He prefers to refuel the regional jets and the turbine equipment and regards the 30-100 gallon tops of the GA tenants as a bother. Obviously 2000+ gallons in a CRJ or 8000 in a B737 is a preferred load. The airport board did an analysis. JetA is competitively priced because the airlines will tanker fuel. 100LL is priced because the FBO can.

        I disagree with your premise. The market is already split was always split. Before it was discontinued, 80 sold for the same price or slightly lower than 100LL or 100. 80 was available at 90% of the airports I flew into, pretty much all except Class B airports, and even then some had it. It is split between turbine and piston.

        Those who can, have moved to mogas from the automotive pumps, test it for alcohol and put it in their airplanes in jugs or from mounted transfer tanks. I have pumped well over 8000 gallons into my plane alone this way. Not because 100LL is too expensive (it is far too expensive), but because it is better for my engine and the environment. Extending my TBO times and spark plug life is a huge bonus.

        • I think you have all the facts, but are blinded by your particular situation. The more split the fuel market is, the less desirable it is to serve, and the more pricing becomes flexible.

          Every penny you might be saving on fuel has already been wiped out by the reduced demand for everything else already in GA (unless you are finding parts at some magical supply tree). We are in a situation where we cannot achieve volume. Had we 70’s level activity, you could have three types of GA fuel at most airports at competitive pricing.

          Of course, the cause is legal and regulatory at the roots, and poor reaction to that in the market. My latest crazy idea is that we move to have private aircraft be treated equally. We could all decertify our planes and start buying the same things used by experimental and military and drones. People on the ground are no more in danger from my plane than any other.

          • A large increase in the price of fuel is just one more nail in the coffin for the average citizen flying.

            For the first time in my flying 40 years of flying I stopped encouraging people to pursue flying and getting their own plane. Why? Because there are now more roadblocks than road.

          • I have switched to MOGAS here in Idaho. It is readily available at many filling stations. I fill a 50 gallon portable tank at the station and pump it into my plane at my hangar. Since using my engine runs smoother, no lead fouling (Clinkers) and it varies from $1.25 to 2$ per gallon cheaper. No normal person and afford to fly with $6 to $7 dollar fuel. I currently pay $3.26 per gallon. When I fly x country I search for reasonably priced 100LL. I NEVER use or have any use for FBO’s with glamorous facilities that charge $2 to $3 per gallon more for 100LL than an honest operator at a smaller airport.
            GA is under attack by the FAA and underrepresented by NBAA and AOPA. Most likely we are seeing the demise of GA and sooner than we think. Buy fuel as cheaply as you can and enjoy it while it lasts!!

  2. This is good news. It sucks that it costs more, but perhaps that will come down once it fully replaced 100LL. Although if we really wanted cheaper fuel we could just replace avgas with jet-A…

    • What good is a cheaper fuel if you can’t burn it in the engines most of the GA piston fleet uses.

        • $50k+ to re-engine existing aircraft to run jet-a engines, or just pay a bit more for a fuel that won’t cause lead fouling? You do the math.

          • The beauty of 93UL is that nothing needs to be done to anything on the plane, no lead fouling, and it costs less per gallon!

            We got stuck with 100LL even though my engine and lots of others in GA were designed for 80/87 or 91. I don’t need or want 100 octane. I certainlt don’t want more expensive 100 octane!

          • That’s a completely different argument. My reply was to the comment about switching all aircraft to use Jet-A.

  3. The price increase they want should be rejected in it’s entirety. I’ll burn leaded 100LL until there’s not a drop left before buying that overpriced product.

    • That is what happened when unleaded auto fuel first appeared. It was priced higher than leaded and acceptance was not final until the 1975 model year when catalytic converter introduction made it mandatory. Still, I find it hard to believe that a substitute for lead has been so hard to find. After all the FAA standard for lead additives in a gas are for a maximum amount, not minimum.

  4. I watched the AOPA interview. They have done some great work but I think the rollout plan needs review. Their plan is to get STCs for almost everything in the fleet. So far so good, I guess. But then each owner will have to buy the STC, stick a new placard to their engine, and insert a POH addendum. I’m thinking that unless the STC is automatically delivered when you buy a gallon, this is going to face huge resistance.

    Maybe the long-term plan is to have the FAA accept G100UL as a full 100LL equivalent.

    • I think that is the hope, but if I recall, GAMI got fed up with how PAFI was set up and decided to go their own route with STC approvals. I would think that if G100UL takes foot across a significant portion of the GA fleet, it will eventually be accepted as a 100LL replacement sans STC.

  5. Aw come on man. All you folks keep forgetting that in just a few years everything will be electric powered and there will be loads of STCs for converting to electric motors and filling fuel tank spaces with light weight batteries. And it will be cheap too.

    • In addition to flying and building full size airplanes, my other hobby is R/C Models. I have been active since 1975 and have competed in many contests flying large models. A few years back, electric power was introduced to R/C. At first it was laughed at, scoffed and made fun of. After a while, it got better, faster and lighter not to mention MASSIVELY cheaper. Today, no serious competitor would even dream of using anything but electric. I have 10 pound models that will take off straight up out of my hand and be out of sight in seconds! I realize that models are in a different environment, but I believe as time goes by, it will just get better and better…

  6. There may be engine health reasons to eliminate the lead, but I wish people would stop trying to make an environmental argument. In the grand scheme of things, avgas is a drop in the bucket. A friend once told me California goes through more mogas in one day than aviation goes through in avgas in an entire year. You’re probably more at risk from radon in your home than lead in your avgas. Peoples’ sense of risk is easy off.

    • If you want some entertainment, Santa Clara County is going to present it’s “lead study findings’ to the community next week in regards to Reid Hillview (RHV). This is prior to a meeting with the county supervisors soon thereafter where they will likely press to close the airport under the guise of lead poisoning.