Is There Room For Two Aviation Fuels?


If you can imagine for a moment an all-powerful criminal mastermind like Bond villain Ernst Stavro Blofeld convening his evil minions for a can’t-miss diabolical scheme to take over the world, what would it be? A fleet of space weapons capable of seizing control of all the world’s airliners and threatening to crash them? Amusing and creative, yes. How about a voracious organism to turn the world oil supply into strawberry jello? I’d prefer cherry myself, but I see the dramatic potential. Or a secret moon base with multi-barrel lasers to vaporize world financial centers? Could work.

A surer bet might be to turn the aviation industry loose on finding a new unleaded fuel and watch—without amusement—at the ensuing uncertainty. I’d describe it as chaos instead, but nobody has enough information to know if it rises to that level or is just plain hopelessness.

So let’s review. As we reported in July, General Aviation Modifications Inc. has a limited STC approval for its G100 unleaded 100-octane fuel. Embry-Riddle has backed out of being a launch demonstration customer for that fuel due to cost, but GAMI and Avfuel, who will produce and distribute it, are confident they’ll find another taker. It will take more than one, of course, so there’s little doubt we’re looking at a long slog to develop the market. Avfuel’s Craig Sincock said as much.

Meanwhile, with the scent of unleaded in the air, will the major oil companies still making 100LL—Phillips, Chevron, Exxon and Shell—hang around to see what happens or take a wrecking ball to their lead shacks before Avfuel (or anyone else) can industrialize G100 for wide distribution? There is profit in refining leaded avgas, but not a lot and it may look less attractive if 100LL really is the sunset product we all think it is.

Meanwhile, the EPA plays the cat in Blofeld’s lap. Will it, as it has been expected to do for years, finally drive the nail in 100LL’s coffin by declaring the aviation industry’s use of lead as a health endangerment? This seems like a foregone conclusion, but we’ve thought that for about 20 years now.

Further caginess comes from Swift Fuel, which has been and is distributing a low-octane UL94 aviation fuel, albeit not widely. Improbably, it announced it’s expanding the market by adding another 47 airports in California to its supply outlets. Still, UL94 remains a market demonstration fuel and with few exceptions, the airports offering it are selling low volumes. Further muddying the mix—but possibly portending competition for G100—is that Swift is developing its own 100-octane fuel, 100R.

If you can see where this is going, let me know. I have no idea and I don’t think anyone else does, either. No one knows if the majors or minors will stay in the leaded avgas business to the bitter end, whether they’ll sign on for licensed production of G100 or Swift’s 100R, if it graduates from development, or if UL94 has legs in the market if 100-octane gains a foothold relatively soon.

Are we about to set the clock back to the days when we had two grades of aviation fuel—three, really—only unleaded this time? Maybe. But it would likely be a highly Balkanized market. “If Swift came out with 100 octane, we would go to that and stop UL94. Most people need at least 91 octane, so that’s so close to 100, we might as well switch over,” Mike Hudetz, who oversees Rochelle Municipal Airport in Illinois, told me when I canvassed a half-dozen airports selling Swift UL94. But the feeling is far from universal. “We are hoping to keep both,” said Spike MacGregor, ops director at Price County Airport in Phillips, Wisconsin. “Some people have said they would rather go back to autofuel,” he adds. So that “both” might include autofuel and a 100-octane candidate.

Swift has a tiny market presence with UL94. According to its website, only about 25 public use airports sell UL94, most centered on the Midwest where Swift’s sole supply source is located in Indiana. The California announcement more than doubled that. Thus far, the fuel has been delivered only by truck, but it may be ramping up sufficient volume to consider rail, which is cheaper.

The airports selling it report that customers are uniformly happy with unleaded fuel and may not care who supplies it. “I’ve paid attention to where we’re going with unleaded fuel. There’s a market for it. People want it,” said Dan DeMeo of Rabbit Aviation Services in San Carlos, California, where the airport has been selling UL94 since 2016. “It’s a lot nicer to work with. I like it better than 100LL,” he adds. Like the other airports I contacted, DeMeo reports no issues or complaints with on-time supply or available volume, which might prove a business model based on low volume delivered from distant suppliers. That’s where GAMI is likely going, at least initially.

Some buyers have equated unleaded fuel with higher prices than 100LL, but that’s not always true with UL94. In fact, it’s mostly untrue. Last week, my price survey found that UL94 was cheaper than 100LL at four of the six airports I checked with, the same at one and more expensive at one. I would call it, then, currently price comparable to 100LL, despite the transportation costs. Even at San Carlos, 2200 miles from the rack in Indiana, 94UL is a dime cheaper than 100LL. (Not having seen the P&L, we don’t know if this pricing is sustainable or set at loss-leader economics.)

What this suggests to me is that UL94 is not necessarily DOA when an unleaded 100-octane arrives, be it G100, 100R or something we don’t know about now. A surprising number of airports already have dual tankage so this isn’t the showstopper I once thought it was. It will likely be driven by the voice of the customer.

“It a hard call to make,” said Brad Stanford, who runs Dublin Municipal in Dublin, Texas.

“There’s always a possibility of two fuels. There’s not enough market research to say. If pilots aren’t constantly hounding them to get this fuel on the field, they’re [FBOs] not gonna do it.”

Of course, the other possibility of a two-fuel world is GAMI’s G100 and Swift’s 100R. Or some other player we don’t know about. And with the uncertain intent of the current 100LL supply world, I wonder if there aren’t going to be supply disruptions as the gaps get filled in, as they inevitably will.

I guess. Somehow, I sense it’s gonna be a long five years ahead.

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  1. As mentioned on a previous thread—we sell 100LL AND aviation auto fuel. The auto fuel is produced at an aviation refinery—it has a minimum of 94 octane—it is only produced for summer month Reid vapor pressure—every load has a “birth certificate “ to attest to the above, and it is only trucked by trucks dedicated exclusively to aviation fuel. We have never had a fuel issue in decades.

    We will continue to sell 100 LL UNTIL there is enough demand and at a competitive price. I expect that to eventually happen/-years down the road. At that time, we will likely re evaluate, and barring operational issues, make the switch at that time.

    In the meantime—I predict that many pilots will move to aviation auto if there is a big price difference. Users will move to the margins—go with aviation auto for those who can use it—or, barring any users difficulties—unleaded 100 octane.

    For most of the country—supplying 100 unleaded won’t be a viable choice if the price is 60–90 cents higher than 100 LL.

  2. “When 100LL is outlawed, only outlaws will use 100LL.”

    That obvious truth aside, as long as these various unleaded products are fungible, it may not matter how many of them are available in any given geographic area.

    Proponents of less-than-100-octane alternatives are of the “I’m aboard; you can pull up the ladder!” persuasion. Their population of aircraft is larger, but the vast bulk of aviation gasoline that is sold goes into the tanks of aircraft that REQUIRE 100-octane fuel.

    So in my simple mind, if we’re going to see a two- (non-jet) fuel ecosphere, it will be:
    1. A panoply of products that provide 100-octane performance.
    2. A panoply of products that provide sub-100-octane performance.

    How many airports will bother to offer one of EACH? If the cost differential is small (say, 50 cents or so), probably none.

  3. Wellcome to the Kingdom of Sweden where Hjelmco pioneered unleaded AVGAS with 80 UL in the year of 1981 and Hjelmco AVGAS 91/96 UL in the year of 1991. We have for our network of 110 airfields/ports produced both the UL sorts and the 100 LL and marketed both of them now for 40 years.
    The market appreciates having the UL AVGAS because it is about 40 USA cent cheaper than 100 LL/US gallon and engines tend to (by 40 years of statistics) operate to about 3000 hours (TBO + 50 %) before the needed overhaul.
    The Hjelmco AVGAS 100 UL was developed in year 2006 and tested with the Swiss Civil Aviation Authority and the German DLR (equivalent to the US NASA). It is also supported by 400 pages of technical documentation originating from Cessna. This fuel now carries 2 US patents plus patents in Canada, Australia, New Zeeland and Europe (granted Aug 04 2021).
    The problem: it was not invented in the US?
    Wellcome to our webb page where there are numerous information in English to obtain.
    Paul is well aware of Hjelmco.

  4. I’m sure not technically savvy here, but how much of the GA fleet operate with an O-360 or smaller, including Rotax engines. I’ve been using auto fuel for the last 20 years in my A65s, realizing they will run on about anything, and have had excellent results with it. Always clean plugs, no stuck valves, etc. I know a bunch of folks say auto fuel is no good, but what’s the track record of it harming anyone’s engines? I haven’t heard of any personal experiences. I say auto fuel for one of the choices.

    • I’ve owned my C182 since 1990. It came with a Gold Medallion Factory Reman (zero time) with 250 SFREM. O-470R. Around that time 80 started going away. I tried a steady diet of 100LL but ended up with fouled bottom plugs about every 50-100 hrs no matter how aggressively I leaned. The engine is a cold blooded engine with CHTs in the low 320s summer and low 300s winter, even in aggressive high powered climbs it was hard to get CHTs above 360.
      I switched to ETOH free mogas at 335 hours SFRM, no appreciable difference in performance, CHTs, EGTS or fuel consumption. The engine ran to 2750 hrs or about 1250 past its 1500 hr TBO. The overhaul was due to increased nickel in the oil and Cam spalling. It ran nearly exclusively on mogas. At teardown, the overhauler told me I’d probably trashed the entire engine. Two days later he said other than the cam, the engine was immaculate.

      I flew between 150 and 300 hours/year at altitudes between 2000′ MSL up to 15,000. Never had a whisper of problems. The engine is now on its second run, at 1750, 250 past TBO running mostly on mogas, which is getting harder to find, a smattering of time on Swift 94UL, and the remainder on 100LL. It flies on the average twice a month on 5.5 hour legs, the oil analyses are clean with no wear metals and more lead than I’ve seen in a long time, mainly due to my second base having only 100LL.

      So, since the 1990s I’ve run around 4,250 hours on this engine, one overhaul, which might have been avoided if camguard was used.

  5. What’s the track record? We’ve sold or used aviation auto fuel for 16 years at this FBO, and 12 years at another. With use/sales at about 15,000 gallons a year, that’s 420,000 gallons without a problem. This doesn’t include what fuel pilots bring in from the local gas station in cans.

    The only issue–since we get all of our fuel straight from the refiner, who MAKES it to aviation specifications, I’d like to get rid of the “odifier” added to auto gas. Use the same odor as 100 octane. The only objection to aviation auto fuel is the odor or car gas.

    • Jim. What’s the biggest engines with an auto fuel STC? What are the biggest your customers have used it with?

      • My C182 with an O470 has a mogas STC which I would have gotten if non ethanol mogas was available in California. Also always fueled it on 80 Octane avgas (which by the way contained less lead than 100LL) when it was still refined.

      • Biggest engines with an auto fuel STC? Some that come immediately to mind:
        O-540 on Cherokee 235 and AeroSpatiale Rallye
        0-470s on Skylanes and 180s
        P&W R-985 of Ag Cat and BT-13
        P&W R-1340 (600 hp.) on Ag Cat and T-6
        R-1830 on DC-3 (skydiver aircraft)

        For those with 160 hp engines, Petersen does have an STC for them–high-test auto fuel (we do that anyway). For Cherokee Warriors, it requires replacing the RH fuel line with a larger line, and a second vacuum pump for standby.

        If you are interested to see the aircraft and engines approved, Petersen has a list here:

    • There’s one other objection besides smell. Aging. Autofuel, even without ethanol, doesn’t age as well as avgas does and the hotter it is, the worse it is. Probably not an issue for a year or so, but longer than that and you can begin to see gum formation. Avgas can sit for years and remain chemically stable.

      So, apparently, can the new unleaded 100-octane fuels.

      • Good point, Paul.

        To protect against age, we only accept deliveries with “summer blend” fuel. The refinery usually switches over to “winter blend” (changed Reid Vapor Pressure) at the end of October each year. To insure that there is no old fuel, or winter blend fuel, we bring the inventory up to 7000 gallons–enough to take us through the winter (yes, the winter in Minnesota is LONG, but not a YEAR LONG!–laugh). We have a floating suction system in the tank to protect against water condensation, as well as a “dead stop” water filter that shuts down the pumps in the event of water contamination.

        In short, we have done everything we can to protect against fuel problems (“birth certificate” for the fuel, dedicated delivery trucks, summer blend only for RVP, floating suction, aviation filtration, no old fuel, water filters). We do it not only to protect our customers, but OURSELVES. Years ago, we had a lawyer flying a T-6 in to get fuel on the way back from Oshkosh–when he got home, he sent a letter saying “I had some engine problems, I may have gotten some bad fuel.” I told him “You picked the wrong guy to tell THAT fairy tale to!

        Moral of the story–we don’t take a chance on fuel from the local gas station. Who knows WHAT it has been mixed with during storage or in the pipeline, or on delivery. Despite all of the extra work, it’s still over a dollar a gallon cheaper than 100LL.

        Now–if they would only change the State laws and do something to eliminate the need to blend in the autogas SMELL at the refinery! (laugh)

      • Isn’t that the truth. Although I use auto fuel in my Aeronca usually, when out away from my airport, I have to use avgas occasionally. And I will say, when I fire it up then, it smells sooo good, like an airplane should.

    • Mogas has issues with storage periods, ethanol and octane ratings, in addition to distribution/delivery issues at airports with limited fuel storage tanks. In California, ALL Mogas must contain Ethanol, and maximum Octane rating for Mogas is 91, so it is a non-starter for most airports and aircraft here. It can be used in some aircraft designed for 80 or 91 Octane fuel years ago, if an Ethanol-free source can be arranged.

  6. Does anyone know why ASTM (the standards group that handles standards for the petroleum industry) didn’t take this on years ago? They have a pretty good track record of creating functional standards for the rest of the hydrocarbon-consuming universe.

    It seems like it would have made a lot more sense to start with a standard that everyone has to meet and that the stakeholders (engine manufacturers, refiners, distributors, FBOs, FAA and other CAAs) accept, THEN have the various fuel refiners or innovators like Swift and GAMI create formulations that meet the standard.

    • You’ve got it backwards, actually. The primary spec was 100 octane. When 100LL came into being, the ASTM spec (D910) was written based on what was known to work, which was a certain amount of lead additive, vapor pressure, net heat content and other qualities. D910 described that and it became more a purchasing agent’s spec sheet rather than a recipe.

  7. Interesting that Swift has lined up so many new California airports–I was under the impression they were actively trying NOT to sell it to airports here before. At the snails pace UL avgas has been coming to market it will finally become ubiquitous about the same time IC engines become illegal due to climate change.

    • Swift was never opposed to sale of UL94 in California. It takes years of groundwork to educate pilots and build demand and streamline the STC process to make it happen. And then it took a major effort to establish a distribution model of large enough quantities to overcome transportation cost issues and reliable supply stream. Pilots at Reid Hillview Airport in San Jose led that effort knowing since 2019 that our county politicians were going to use “lead poisoning” as an excuse to close the airport. If you have airport opponents in your neighborhood, rest assured they will be studying Reid Hillview and planning to try and use the lead argument as an excuse to redevelop the airport into a housing tract or shopping center.

  8. STEM be damed, there is no support in communities nor the government for small private piston singles. Heck, even a lot of airports shun smaller planes (so much so that even the sleeping AOPA woke a bit to look at the ramp practices)

    Basically we will get what we get and are supposed to respond with thanks.

  9. As part of the team that has brought Swift UL94 to San Jose CA (and other local airports signing on..) there is no chance that 2 unleaded 100 Octane fuels will remain in the marketplace. Either Swift or GAMI’s formula will be blessed fleetwide by the FAA and will be licensed by the few refiners interested in brewing Avgas to replace the outlawed 100LL. The FAA, EPA and Biden Administration will ban Tetraethyl lead and its importation from Innospec in the UK as soon as the ink dries on FAA approval of UL100. It appears that Phillips, Shell and others are more interested in “green jet fuel” than Avgas, and are not really pursuing the development & testing needed to get final approvals. And if both GAMI and Swift get FAA approvals at or about the same time, the lower-cost formula is going to carry the day, assuming the license terms for the proprietary formula are reasonable.

    • Fully agree–”
      We will continue to sell 100 LL UNTIL there is enough demand and at a competitive price. I expect that to eventually happen/-years down the road. At that time, we will likely re evaluate, and barring operational issues, make the switch at that time.”

    • Once an unleaded 100LL replacement becomes readily available, I don’t know why anyone would voluntarily continue to use 100LL. The reduced maintenance costs and improved reliability of not having to deal with fouled plugs will make up for at least some of the increased fuel cost.

  10. “Are we about to set the clock back to the days when we had two grades of aviation fuel—three, really—only unleaded this time?”

    Are you getting so long in tooth that you have forgotten the time when four grades were available?


    • Not to mention that many older engines were certified on “73 octane fuel” (not specifically identified as an av fuel. In the case of the Ranger engines on the PT-19 and PT-26, it says “If 73 octane is not available, use 65 octane and monitor.”

  11. For what it’s worth:

    Our local Sheetz now has ethanol free 90 octane, on two pumps. Last I checked $3.60/gallon.

    They just finished a remodel on the store, replaced all the old fuel tanks, installed new pumps.

    So logistically/financially, they have found a way to carry an oddball grade in addition to the “normal” stuff.

    We do live near the water, lots of boaters, so that may have factored into the decision. And of course, fuel for lawn equipment. Saves me from going out of my way to the marina to pick up a few gallons for the lawn mower.

    Even further, made a trip to Virginia a month or so back. Their Sheetz had your normal selection, and like 3 other grades/blends at each pump, that I had never seen before. Was very confusing.

  12. I contacted about the target price for 100UL and told it was something less than $100/gal.
    This will only sell if 100LL is outlawed. Does anyone doubt our fuel will be $10/gal or more?
    Many airports in NV and AZ have no fuel, expect more to follow with this price increase.

    • Ray- I have no idea who you contacted, but the refinery cost for Swift’s Unleaded 100 formula is pegged at about 50 cents more per gallon than 100LL. Their UL94 is actually cheaper than 100LL at the refinery, and local airport retail prices driven by transport cost and markups. UL94 is selling in San Jose today for 30 cents more per gallon than 100LL. GAMI’s formula is more expensive to brew, and is forecast to be closer to $1 per gallon more than current 100LL. There were proposed formulas from Phillips and Shell back in PAFI testing cycle prior to 2015 that were very expensive, but those are not viable contenders, as they also happened to dissolve aircraft paint.
      And you can be absolutely sure that as soon as an Unleaded 100 Octane Avgas is “FAA Approved” the federal government (EPA and FAA and Commerce Dept) will outlaw importation of Tetraethyl Lead and 100LL will disappear very rapidly. And lastly, the problems in Nevada and Arizona regarding fuel supplies are directly linked to shortage of Commercial fuel tanker truck drivers, who lost work when COVID reduced driving and flight hours, and thus demand for auto gas and avgas. Chevron here in California has plenty of 100LL, but they and distributors like Avfuel and World and Epic are not very good right now getting it delivered to airports.

  13. Leaded fuel has no future. When not if, it is outlawed, there is going to be chaos as I just don’t see the change over until the issue is forced by a government ban on leaded fuel.

    The number one issue the alphabet groups should be working on is to advocate for a reasonable sunset period to allow an orderly change over, but piston GA has no real political power.

    Personally I think the future is 94 UL. It is the existing 100LL but without the TEL additive. No lead 100 Octane will be so expensive that most aircraft owners will elect to modify their engines for 94 via STC’s.

    • There are only 5 refineries brewing 100LL in the US today. It doesn’t typically flow through any of the major pipelines, to avoid contaminating other fuels with lead. Both of the Unleaded formulas (GAMI and Swift) for 100 Octane are “intermixable”, so as soon as a refinery loses access to lead because it is banned and converts to Unleaded 100, they can ship that to airports and it is a drop-in fuel.. Converting a turbocharged high-compression engine with magnetos to run UL94 would cost a lot of horsepower, and possibly still run poorly at high altitude on hot day. UL94 really is a “bridge product” to reduce lead and take lead away from airport opponents until the universal UL100 is on the market..

      There won’t be a long change-over process. In San Jose, the storage tanks at the FBO’s were allowed to empty, the UL94 was dropped into tanks and pumped into trucks, and aircraft began adding UL94 into fuel tanks the next day. Within a few days, the remaining 100LL was essentially flushed out after a few refuelings. And trust me, the AOPA, NBAA and EAA are all very involved in issues over lead and Avgas.

  14. “If you can see where this is going, let me know. I have no idea and I don’t think anyone else does, either. No one knows if the majors or minors will stay in the leaded avgas business to the bitter end, whether they’ll sign on for licensed production of G100 or Swift’s 100R, if it graduates from development, or if UL94 has legs in the market if 100-octane gains a foothold relatively soon.”

    The market is responding to a very confused end user. Just look at the responses on this thread plus the recent unleaded avgas poll. Some pilots, aircraft owners, and many mechanics swear they can determine “engine damage” in aircraft engines that use non-ethanol auto-gas or mogas. That “engine damage” is never clearly defined. But they swear non-ethanol autogas or mogas is causing some sort of engine anomaly, wear patterns, with their intuition saying it is not good. Sort of an aviation urban myth. No one knows where the myth started. But by gosh, non-ethanol autogas is no good for airplane engines. The hell with the Peterson STC or EAA STC, it don’t matter how exhausting and strenuous the test(s), no matter the accumulated data over the past four decades, non-ethanol/unleaded auto fuel or mogas is no good. Period!

    Then there are those like myself, who has been using non-ethanol auto fuel for a long time ( 15 years in two personally owned airplanes) along with dozens of other fellow aircraft owners, who have clean oil, no fouled plugs, clean valve guides, much cleaner valve seats resulting in much improved compression ratios, lower oil consumption, consistent mag checks, easier starting hot or cold, and averaging $1-2.00 less per gallon fuel costs. The total aircraft engine improvements make it very worthwhile to do whatever is necessary to use non-ethanol autogas, purchased locally from a variety of self-serve stations including Walmart. Yes, not quite as convenient as the local self-serve avgas dispenser. The upside is I don’t have to deal with the nuances of the avgas dispenser that seems to have a mind of its own with no guarantee it will dispense today as it might have a week before. Cross county flights take more planning. But for me, a 20-50 NM diversion for mogas still makes it worthwhile. As both an A&P, an aircraft owner using unleaded, non-ethanol auto fuel over a long time, I still have never convinced the naysayers described above of its virtues. Apparently, the long term testimonies from the EU also do not count to these people either.

    Then we have the third end users who are listening to the debate like spectators viewing a tennis match from the sidelines near the net. They watch the volley’s between the folks who swear mogas is no good and those who are successfully using the same for decades, being mostly renters who fly airplanes having no choice in what fuel is in the tanks. All they know or want assurance of is the engine run properly throughout the flight. Whatever morning sickness or mag roughness will be fixed by a mechanic. Their hourly rates have not changed no matter what is in the tanks. So why get up in a lather over the debate or invest themselves in learning the science to make more educated fuel decisions. In a practical sense, they have no choice.

    The last group is the engine manufacturers. They have a potential liability problem, according to their lawyers, type certificates, the FAA, and many of their engineers. So, they are the last ones to give any kind of blessing using non-ethanol auto fuel, mogas, Swift, Gami, or anybody else’s fuel outside of 100LL avgas. This provides much cannon fodder for the group that swears anything short of 100LL is causing engine damage, adds confusion to group three watching the debate, and frustrating the hell out of those who have been using it for decades. Hence” If you can see where this is going, let me know. I have no idea and I don’t think anyone else does, either.”

    That leaves the manufacturers of avgas having to guess who will be their most loyal customers will be. No doubt they are keeping an eye out for companies like Swift or GAMI while raising the proverbial finger into the air to see how those competitors financial winds are blowing combined with a distant curiosity to watch their investment into the infrastructure in their attempt to broaden their distribution. All of them know how to make unleaded mogas and non-ethanol auto fuel. Its just a matter of deciding when it is time to join the party or spoil it.

    Personally, I will not discontinue use of my local Walmart’s 91 octane non-ethanol auto fuel especially if my unleaded alternative will be as expensive or more so that avgas. If my airport will stock mogas that is less expensive than 100LL, I will happily use it. I already seek and use airports that have made that investment. But as long as general aviation is as fractured as it is, I see no wide implementation of unleaded fuel for a long time.

    When the manufacturing of new airplanes and their engines out pace the use and eventual destruction of the 66-70% of the present 40-80 year old airplanes that can already use mogas, that is when the debate will be settled. But that means 100LL will be required by the big inch Continental and Lycoming owners because I don’t see those engine manufacturers willing to invest in making those engines work on anything less than 100LL. By that time, the aircraft ranks will have shrunk so much that there will be no financial reason to continue production. The EPA, average non GA flying citizens, and aviation clueless politicians already look at any privately owned airplane as an extravagance. Extravagance and “green” don’t mix.

    At my age, I have no fear of losing 100LL. I chose to own airplanes that run excellent on readily available non-ethanol auto fuel. That was a driving reason why I bought what I did. I have a solution that is “green”, less expensive, and far better for my engine. It is readily available. And my airplane performs as well or better than the million dollar airplanes that cannot fly without 100LL.

    So, I will let the battle for a “green” fuel be fought by the 200-400 per year new Cirrus owners, the remaining used Cirrus owners, the Lycoming owners who cannot gain an auto fuel STC, Swift, and GAMI. Plenty of potential room for two fuels. However, I see no end to the confusion nor the debate.

    • Jim- If you can find reliable supplies of Mogas without ethanol and your aircraft are covered by Mogas STC, that will continue to remain an option for you and your airplane, though often without dedicated fuel tanks and deliveries at the airport. There is only going to be a single unleaded 100 Octane Avgas fuel on the market within a couple years, and that will be the standard at most larger airports in the US. Swift has made clear that they will replace UL94 with Unleaded 100 Octane as soon as the FAA has completed testing and approval. The government and regulators will not permit 100LL to exist for planes anymore than they permitted lead in auto gas after the new formulas were available.

  15. Paul may or may not remember, but over 15 years ago I suggested that we only needed one fuel, the fuel that was currently in production… 100LL. BUT DON’T ADD THE LEAD.

    Have the lead (TEL) added at the pump (if 100+octane is really needled).

    Before the TEL is added, the fuel is about 94 octane (essentially 94UL) and absolutely 100% compatible with all aircraft systems. All but the highest compression or TSIO engines can use it TODAY. Those that need the lead can get it (and pay for it) at the pump.

    Overnight we will have eliminated 70%+ of aviation lead emissions and provided a RELIABLE source of Unleaded AVGAS that is cheaper than leaded AVGAS.

    Now, the engine manufacturers have a reason to dust off their TSEIO engines and finally get them certified.

    Operators will have a reason to buy the new engines (cheaper gas)

    And, Operators who don’t need or want it won’t be forced to pay extra for octane they neither need or want.

    “Dial an Octane” is not a new concept, it was used at automobile gas stations for decades. We just need an updated version.

    For decades, AOPA has been championing the “one-fuel solution” as the only solution. 30 years later, we’re still needlessly pumping lead through engines that don’t need it (or 100 octane).

    • Providing 94UL will not eliminate 70% of lead emissions. It’s more like 30%.

      While it’s true that 70% of the existing fleet can run on low-octane fuel, they’re made up of small(er) planes with smaller engines and consequently less fuel consumption. The remaining 30% of the fleet consists of bigger engines that require 100 octane and are used more in commercial operations. As a result they consume about 70% of avgas sold.

      • Kirk – The 70% of existing GA piston fleet that can burn UL94 might consume a little less fuel per hour, but they fly significantly more hours per month or year than the aircraft with larger engines.. At our airport in San Jose, CA 90 of the airport operations tracked by the control tower over an entire week were aircraft were aircraft eligible to use UL94. We believe the airborne lead emissions reduction by switching to UL94 is closer to 80%, not 30%…

        • That may be true based upon your observations at one airport. But fleet-wide surveys done several years apart have repeatedly shown the 70/30 mix to be about right (ie. 30% of the fleet can only burn 100LL, but they consume 70% of the avgas sold).

          Much of business aviation is invisible to the average private pilot because it occurs during the work-week (and at night) and and not just on weekends. The local airport may seem alive and buzzing with training activity and weekend flyers. But there are a lot of high-horsepower piston singles and twins flying away from the local area, delivering passengers and freight to and fro.

  16. Today 8/31 the UN declared victory by announcing the world is free from leaded gas (in trucks and cars). It took almost 100 years for this to happen. Interesting since unlike aviation, cars didn’t have the technical hurdles: a country could’ve switched to unleaded in the 70s.

    I think the only way to accelerate unleaded in aviation is to set a short government compliance timeline and subsidize the adoption of it.

    NOTE: before anyone comes crashing down on this post, I’m just saying that is a path not necessarily what I advocate or prefer. Just saying what it would take.

    Think of as lol the subsidies we already are paying for. This would be one more.

  17. As Kris Larson and RN have indicated, there are suggestions about reducing the amount of lead in fuels, but it may also indicate the handwriting it already on the wall. With a single producer of TEL for the world (practically speaking), three things could happen to end that production. First, a fire or similar accident at the production facility. TEL is nasty stuff; both a health hazard and highly flammable. Damage to the facility might make them decide to just not rebuild. Second, declining sales from issues like the UN elimination of lead in auto fuels and/or aviation fuels might cause them to halt production. Third, the threat of government (i.e. EPA, etc.) mandates might just force the same outcome as #2. Why stay until the end if the outcome is obvious? Why continue to pay O&M costs on equipment for a product in serious decline? I fear the best we can hope for is an orderly transition from 100LL to one form of 100UL before the proverbial iceberg hits our ship. One way or the other, it’s coming.

    • Yes, Innospec in the UK (sole producer of Tetraethyl Lead..) is very much a risky supplier. They are under pressure to close the facility, and they have declared publicly that they would like to shut down the facility themselves, but are compelled to keep making the product solely for Avgas. That is why I am so confident that 100LL will disappear very rapidly as soon as unleaded 100 Octane fuel is approved. If the plant were to experience an unplanned shutdown, the world’s supply of Avgas would indeed be at risk, and a lot of planes would be grounded.

  18. The switch to UL100 could be a disaster for many owners of airplanes produced in small volume or for those whose manufacturers are now defunct. Many will run just fine on UL100 or 94UL or mogas, but specify only 100LL on their original airworthiness certificate. Presently, if I understand it correctly, this can only be changed upon petition and proof from the airframe manufacturer. (Approval by the engine manufacturer alone is not sufficient.) Even if the original manufacturer exists, what motivation do they have to make such an effort – one that earns them nothing? Going the STC route is not a much better alternative when the sales potential may only number in the dozens.

    Hopefully, the FAA will declare UL100 or whatever as a functional and legal replacement for 100LL without the potential paperwork nightmare which will otherwise follow. Or potentially worse, the grounding of hundreds of perfectly good airplanes, including mine.

    • It could depend on exactly how the original certificate was worded. If the certificate said that the fuel was to be 100LL, or similar wording, you might be correct. If the certificate said 100LL or 100 octane aviation fuel, then as long as the FAA approves the 100UL formulation, you should be legal. The latter wording would accept any approved fuel of 100 octane rating, regardless of the presence or absence of TEL.

    • The switch to UL94 for older airplanes is relatively simple if the aircraft and engine combo are eligible per Swift’s Testing and Approval process. A quick search on their website will identify whether the plane and engine combo are OK or not <and you can send inquiry of combo not listed..) and then if you are eligible, purchase the $100 STC package, get pre-filled 337 forms for any A&P to make logbook entry and put stickers next to filler caps. The Swift UL94 STC's will also extend to their UL100 fuel if it becomes the standard. They are following different path than GAMI, by trying to complete broadest possible testing and approvals (making it universal replacement for 100LL) before launching publicly. FWIW, all but one of the GAMI 100 Octane unleaded aircraft/engine combo's are also approved for UL94…

  19. Many years ago I was having our R-985 overhauled at a well known shop in Oklahoma. I wanted to watch the tear down & watch the magna fluxing of the crankshaft as I was aware of the possible problems with those crankshafts. While they were tearing down the engine the owner of the shop asked me “what oil are you using?” I answered hime & added that I was religious about changing it every 25 hours (non-filtered engine). He said he’d “never seen one this clean”. He pointed to a bin full of cylinders & told me that he “could tell if the engine had been run on auto fuel”. I look at a couple of cylinders & saw severe pitting of the cylinder walls. I will continue to use aviation fuels which do not cause my cylinders to be put in that bin. The cheapest thing you do to an airplane engine is put fuel & oil in it.

    • One problem with auto gas is that there is no consistent chemical formulation across the various producers. All refiners will produce an automotive grade fuel, but the exact chemical content depends largely on the base crude stocks they start with. Since there are many hundreds of crude oils from different suppliers, a refinery must mix and blend to create a fuel that meets ASTM specifications. However, those specifications primarily define physical attributes such as minimum octane rating, maximum Reid vapor pressure, etc., but don’t limit the chemical content very much. So, depending on your location, you could have a “Mogas” that is distinctly different in chemical content from other parts of the country. All this to say that people’s experiences with using auto gas in their plane engines, good or bad, may vary depending on which gas they are using. On the other hand, 100LL has a much more restrictive chemical base, so fleet wide variations are pretty small. Bottom line, if you have a good history with Mogas, great. But don’t make the assumption that all engines and all auto gas will be compatible. As you say, Avgas and oil are cheap compared to an engine overhaul. Experiment at your own risk.

  20. The whole 100LL is doomed camp seem pretty suspicious to me. You know what’s doomed? Certified light aircraft over fifty years old. Using similar logic, let’s see how this goes.

    Everything you guys say about 100LL is more true about most of the fleet. What causes more deaths? Untraceable amounts of lead even near the runways or the planes themselves?

    There’s really no reason the FAA hasn’t started an inspection regime on most of the older aircraft that would make them more expensive to operate than simply replacing them with a new bird.

    Think the EPA has an agenda? What about Textron? Those guys would LOVE to quadruple sales of new aircraft. Their lobbyists likely get paid money the bureaucrats would drool over.

    So how about we take the certitude down a notch?

  21. Eric- The fleet of “elder aircraft” is way too large to scrap, and the the FAA really has no interest in grounding airworthy airplanes. Folks need to understand that an army of environmentalists, anti-airport crusaders and bureaucrats have discovered that little airplanes burn gas with lead in it, and all lead in the environment is harmful. The FAA and EPA have known that since the 90’s, and sparred in a few court cases, but with rising pressure against lead and rising anxiety over single source in the UK, there is finally momentum to bring UL100 to market. And when it arrives, UL100 will roll out worldwide pretty fast as the new single Avgas for piston engines aircraft…