Confused in Texas

Recently we heard from an exasperated reader from a major general aviation airport in southeastern Texas. Like many of his fellow recreational pilots in the Lone Star state, he had asked his new airport manager for help getting mogas onto the airfield as a means to lower the cost of flying. He had even gone to the effort to find a surplus fuel tank and a supplier of aviation-grade mogas (ethanol-free, 91+ AKI). The response from the airport’s manager is sadly typical of the confusion that remains prevalent in aviation. I have paraphrased this below:

“He said that since the airport is a federally-funded, the Texas Department of Transportation won’t let them put in mogas because they lose their federal grant money. He also said that the planes that have the STC to run car gas are not allowed to run car gas since it’s not an FAA-approved fuel.”

Where does one start with this statement?

First, according to GAfuels co-author Dean Billing’s accurate list, there are at least six airports in the state of Texas offering mogas. Three of these are publicly-owned.

Second, the whole point to an FAA-approved mogas STC is to permit aircraft to operate on mogas. Some 60,000 such STCs have been issued by the EAA and Petersen Aviation since 1982. Nearly all new aircraft engines developed in the past few years may be operated on mogas according to the TCs and do not require an STC; the best such examples are the ubiquitous engines from Rotax and Jabiru on the latest generation of training and LSA aircraft.

Lastly — and this is an important point — the FAA does not approve any fuels; it only approves engine/airframe combinations to operate on fuels defined by organizations such as the ASTM. For instance, 100LL is defined by ASTM D-910 and mogas (gasoline) by ASTM D-4814. Mogas TCs and STCs have additional requirements regarding the AKI rating and the prohibition of ethanol.

During AirVenture 2011 I met by chance the new manager of general aviation for one of the nation’s largest avgas suppliers, coincidentally the same company that delivers avgas and Jet-A to the airport mentioned above. When I asked him why his company would not deliver the same premium, ethanol-free fuel that they supply to many gas stations, he looked confused and stated that the fuel for all piston aviation engines was required to contain lead. Over the following several weeks, I slowly educated him on the long, successful history of mogas as a legal, safe aviation fuel and the fact that the vast majority of the current piston-engined fleet can operate on it. In the end, he admitted his previous ignorance but used the typical excuse that his company’s lawyers would not allow its sale.

When confronted with confusing, contradictory statements from aviation officials, we would always advise our readers to kindly ask for written evidence of the purported facts or regulations. We’re happy to help set the story straight as we did in these two instances. Clarity is the first step towards progress.


  1. Mark C says

    This is an old thread, but in case anyone comes across it like I did, I’ll add my .02. For everyone who says they don’t want to haul 5 gallon cans and pour them into the airplane, feel free to steal an idea one of my partners put into place for us. Fuel transfer tanks, electric pumps, and flow meters can be bought pretty cheap new and even cheaper used, under $2000 for the parts to set up a brand-new 200 gallon fueling station, under $1000 if you go with a 116 gallon solution. Sure, you may have to wink at a few placards saying the tank isn’t intended for use w/gasoline and may not be approved for on-highway use, but those are CYA’s and mostly aimed at commercial operators. If you rig the tank with a wheeled dolly, it can be rolled into an enclosed trailer and taken to a gas station selling ethanol free fuel and filled, and if after the initial fill you bring a couple 5-gallon cans and (easily and quickly) dump them into the storage tank every time you visit the hangar, you never have to haul it again. Do make sure the pump itself is rated for use w/gasoline, that’s a rule you don’t want to break. Most of the motors are 12V and easily powered by one of the portable “jump packs” used to start cars with dead batteries, which can be taken home and charged if necessary, or charged in the hangar if you have electricity. With a $2/Gal differential in fuel prices, and it’s often more, the whole system pays for itself in 50 – 100 hours of flying a Cessna 172.

  2. George says

    As seems to be the norm – if you have an airport manager who is not a pilot, brand him as a political hack, then go on to paint a picture that implies that all, or at least many, airport managers fit that mold. I am an airport manager who is a pilot, designated the hard earned Accredited Airport Executive (AAE) and have attempted to get the FBO to provide mogas. No luck with that, so do we now paint all FBOs as no good anti aviation sluggards? The invitation to provide mogas has been extended to any pilot or group who wishes to do so at this airport. No takers. I also do not like hauling jerry cans to pour into my aircraft, low wing though it is. Every airport manager has a boss, and if he is unreasonable in any regard there are avenues of redress available. USE them, and quit complaining that nothing can be done. Get off your behinds and do it!

    • Kent Misegades says

      Approximately 120 airports currently sell mogas in the U.S., and this number has been slowly but steadily rising. Many airport managers are open to alternative fuels, but that alone will not guarantee the success of mogas, or any other fuel for that matter. We have helped dozens of open-minded airport & FBO managers as well as countless airport commissioners the past several years, and many face numerous challenges. Many grassroots pilots have rolled up their sleeves and opened their wallets to bring mogas onto their airfields. They all deserve our compliments. What is frustrating are the closed-minded aviation leaders who are unwilling to consider anything new, although “new” hardly describes mogas. The amount of utter nonsense that is reported, even in leading aviation journals (other than GAN of course), concerning mogas is the most frustrating – despite the best efforts of mogas supporters many people in aviation are simply unwilling to review the facts about anything not found in their avgas and Jet-A tanks. Some of the worst offenders are in fact the suppliers of avgas. Is mogas for every airport? No, but neither is Jet-A or even Avgas. Let’s let free markets make these decisions and stop attempting to dictate a one-size-fits all solution on all pilots and all airports.

  3. Jamie Beckett says

    Well written, Kent. You cover a lot of ground in this one, and you cover it well. Ignorance is a problem, indeed. With continued education, like you provided in this piece, the industry will come around. Keep up the good work.

    • Kent Misegades says

      Thanks Jamie. I have some excellent sources in industry who check my work, as this is such a critical topic.

  4. Jeff says

    I have a STC for mogas, but my airport doesn’t carry it. They cite a number of reasons.
    They don’t have the tanks and fuel supply equipment for a third fuel.
    Their Jet A and Avgas supplier won’t allow it.
    There is a small need for it. After all everyone can use avgas but a smaller number can use mogas. So the economics don’t pan out.
    They also cite the mark up on avgas is pretty good.

    What we need is the alphabet organizations AND the FAA to PUSH the use of mogas at GA airports. Disseminate proper info on who can and can’t use it. Let the EPA give grants for the airports to get the dispensing equipment. It would be cheaper than getting the lead out otherwise.
    I also have a sneaky suspection the producers of avgas are not for mogas as they would lose the exclusive market and the market would drop precipitously, which in turn may make avgas much more expensive, or some producers would leave the market altogether.
    Frankly I use avgas because I simply am not interested in hauling in 5 gallon jerry cans of mogas, climbing a ladder and slowly pouring it into my plane.

    • Kent Misegades says

      Jeff, these are some of the more typical excuses. Here are some thoughts to get mogas onto your airfield:

      “They don’t have the tanks and fuel supply equipment for a third fuel.” – Mogas needs are very modest, a 2,000g self-service fuel system is plenty and can cost well under $50K. Private financing is readily available for 100% of the system including site prep. It will pay for itself in 3-4 years and requires nearly zero maintenance and personnel costs.

      “Their Jet A and Avgas supplier won’t allow it.” – That is illegal, restriction of free trade. Assuming you are on a public airport, FAA Order 5190, chapter 8, forbids granting of exclusive fuel sales rights to one company, FBO, etc. The avgas supplier has no say whatsoever what other fuels are sold. Ask them to show you the regulation – they can’t.

      “There is a small need for it. After all everyone can use avgas but a smaller number can use mogas. So the economics don’t pan out.” – Just the opposite is true. Well over 80% of all piston aircraft can legally and safely operate on mogas. Margins for mogas and avgas sales are the same to FBOs, but selling a lower-cost product will lead to more sales and overall higher net revenue to the airport. It is basic economics. Many airports offer Jet-A but have no turbine aircraft based there, why? Speculation that it will attract more business, the same for mogas, but the cost to add Jet-A fuel systems and refuelers is very high compared to mogas.

      “They also cite the mark up on avgas is pretty good.” – Yes, the dirty secret of anti-competitive attitudes at airports. But the margins on mogas are the same. Since it costs less to the pilot, they will sell more of it than avgas and make more money. Same as taxes, lower rates and tax revenue climbs. Increase tax rates and tax revenue drops. ECON 101.

      Lastly, why wait for the airport to do this for you? Find a few investors and install your own mogas system if the airport does not want to do it. FAR 5130 allows you to do this. contact me at for more ideas.

  5. Dustin Paulson says

    Would it be possible to get the base fuel stock used for making 100LL before the lead is added? My past experience with Mogas has been that it’s shelf life is far more limited than what I’ve seen with 100LL. When I have purchased it at airports that have it, and don’t sell (turn over) their supply quickly, it will have that distinct objectionable “old gasoline” odor to it, rather than the sweet clean smell of 100LL, making me question whether I should have purchased it. My understanding is that the base stock used for making the 100LL fuel has approximately a 94 AKI before the lead is added , and it seems that the avgas base stock would be more pure, and hold up better over time with less chance of turning to the varnish that mogas seems to if left sitting too long, thus gumming up the fuel system.

    • Greg W says

      What you are asking about with the 100LL base stock is the FAA 94UL avgas, ASTM 7592-2010. It was a relatively early attempt at the “drop-in” replacement fuel. The problem was the aircraft that needed the higher octane rating. The pour point, vapor pressure etc. all very closely match 100LL as that is what it is just with out the lead. The tet. lead is added at the end of the refining process and so the ASTM 7592-2010 fuel is made already and then changed to D-910 spec by adding the lead. This would be a technically simple fuel to put in use, basically where the old -80, 91/96 avgas was, politically not so easy. No STC would be needed as it is “avgas” and most if not all T.C.’s require “avgas”, not a specific ASTM spec. My aircraft for instance was certified in 1945 on Army 73 octane avgas, a gasoline not produced since the early ’50’s. It is fine with the FAA to use the “next higher grade” hence the use of 100LL without an STC.

      • Dustin Paulson says

        So why not just have it available instead of mogas???

        It appears that it would be usable in all the aircraft that mogas is usable in, probably give better performance in those higher performance engines that are on the lower edge of their limits when using mogas, prevent the valve sticking in some of the lower performance engines caused when they use 100LL, not require an STC, and hold up much better long term in both the storage tanks, and the aircraft tanks as well.
        It just seems like a winner from every aspect when compared to mogas.

    • Kent Misegades says

      Greg W does a good job explaining what this fuel is, and this idea has been well vetted. The main problem with this as I see it is that we would be creating yet another boutique fuel. The only way to truly lower the cost of flying is to use commodity products as much as possible, for instance auto engine conversions, iPads for cockpits, and gasoline or Jet-A for fuel. We spread our costs over a vastly larger group of consumers. Plus, the infrastructure to deliver mogas is enormous – there are 110,000 gas stations in the U.S. There is plenty of ethanol-free fuel at the same terminals where it is blended with ethanol before being delivered to gas stations, marinas, airports, etc. It makes far more sense to me to adapt engines to commodity fuels than to create new fuels for a tiny number of aging aircraft. 60,000 mogas STCs shows this is possible. Jet-A burning aircraft diesel engines show this is possible. Logic says this is the only way to go, two fuels, mogas and Jet-A and modify those planes that can not operate on either. Nearly all new airplanes can.

      • Greg W says

        Kent thank you for the response. I fully agree with any avgas being a boutique fuel that cannot come close to mogas in production/distribution costs. My point with the 94UL was that it is being made it just never leaves the refinery and that as a listed avgas no STC is needed. The Avgas label as opposed to mogas or auto gas would also ease the minds of many pilot/operators who are nervous about the use of mogas,as you’re article alluded to in the case of the airport manager. Mogas would surly be the easier fuel to distribute because it is already in distribution and the economics would not allow 94UL to be distributed because 100LL works for everyone from the producers viewpoint so why change it. I gave up on my local airport board after three years, you have a national voice so please keep trying.

  6. Rich says

    This is the problem with so many airport managers.
    They don’t fly so they have no interest in educating themselves about the industry in which they want to make a living.
    They are just ignorant.

    And so many are politically appointed hack jobs that are so dumb they can barely find their way to work let alone know anything about fuels and aircraft.

    Then you get the “salespeople” that are in the same boat.
    They can sell but they have no interest in aviation only their commission checks.

    They only spout out a few facts that they have managed to remember from the brochure that was put together by more marketing people that are even farther away from the front line users than the sales people.

    But it is the ineptness of many of these airport managers that are the last line of defense in saving and promoting GA.

    This makes me sick.

    • Kent Misegades says

      In many cases the only solution is to go around these barriers. Start your own fueling business. If the airport management says this is not allowed, demand to see the regulations that forbid it. If they have written exclusionary clauses into the airport’s Master Plan (Minimum Standards) to protect existing FBOs from competition, convince the airport commissioners that this is illegal (FAA Order 513) and anti-competitive. Then go out and do it yourself with your friends, investors, airport tenants, EAA chapters, whatever it takes.

  7. Terry says

    Would users of mogas mind paying the airport fuel flowage fee that FBOs and businesses self fueling are required to pay (typically $0.05 – .10 per gallon)?

    • Rich says

      They already do.
      Airports that sell mogas on the field certainly do not exempt the buyers from the flowage fees.
      Mogas sold at an airport is about 50 cents or more higher than down town.

    • Kent Misegades says

      All sellers of any aviation fuel – mogas, avgas, Jet-A – typically pay the same flowage fee to the airport. 7 cents is the average. They also pay the same 21.8 cent/gallon federal aviation fuel tax. If people self-fuel, they are paying federal state and highway fuel taxes which does not help aviation at all!

      Do not compare the cost of mogas at an airport to the cost of pump gas, there are many factors involved here. Mogas should be 91+ AKI, contain no ethanol, and delivery volumes are smaller which drives up delivery costs. Taxes too are different, with aviation taxes being lower than combine federal and state highway fuel taxes. More important is the cost of mogas at the airport compared to cost of avgas at the same airport. According to AirNav, this difference is on average $1.38 right now. Pilots will deviate a route to save 10 cents per gallon, so this differential is huge.

  8. says

    Useful article, thanks Kent!
    I’ve seen this confusion at airports all over the place. My suggestion would be for U-Fuel or similar organization to develop some online and in-person training materials to explain the rules and current industry state to FBOs (and Avgas dealers!) Let’s get some education going!

    • Kent Misegades says

      Len, that is why we created the Aviation Fuel Club two years ago. See its newsletters here for details:

      See also 3+ years of articles in this blog which cover most aviation fuel topics, especially for piston aircraft.

      Avgas sellers for the most part have shown no interest in mogas, despite our efforts to educate them. Don’t waste your time on them. The same holds for the aviation alphabets, with the notable exceptions of our friends Dan Johnson of LAMA and Roy Beisswenger of USUA. The EAA, AOPA, NATA, GAMA, and NBAA are doing nothing to promote mogas, despite our efforts to educate and encourage them.

      Their disinterest is the reason that Mark Ellery, an Aviation Fuel Club member and avgas distributor, just started Airworthy Autogas, to deliver aviation-grade mogas to airports. Support his business if you want to see this situation change.

  9. Dietrich Fecht says

    Thanks for the information.

    “… FAA does not approve any fuels; it only approves engine/airframe combinations to operate on fuels defined by organizations such as the ASTM”.

    Does this make clear that new aircraft which are designed and built to be operated with ASTM automotive street fuels, with ethanol content too when the planes are designed and built for this, could be approved by the FAA and flown legally with ASTM defined automotive street fuels which are used to operate both, cars and airplanes?

    For expample experimental aircraft? And future §23 certified airplanes too?

    • Kent Misegades says

      Yes, in fact the Rotax 912 series aircraft may operate on mogas containing up to 10% ethanol. This does not imply however that the airframes for which they are used can tolerate ethanol – it is always an engine + airframe combination that counts. Essentially, anything that comes in contact with fuels must be considered, from the tank to the cylinders. Experimental aircraft owners are free to use any fuel they wish. Safe pilots however will follow the same guidelines as for certificated aircraft. The best is to find one that closely matches your homebuilt and follow the TCs or STCs for it. When in doubt, always opt for the highest AKI, ethanol-free gasoline from a branded seller. Always test for ethanol and use quality filters.

    • Kent Misegades says

      Note also – not all aircraft using the Rotax 912 are certificated for ethanol blends even though the engine is! Another example – the Jabiru engines are certificated for up to E10, but the Jabiru aircraft are not, anymore. While the composite fuel tanks were sealed with material that was suppose to tolerate the fuel, after extended use some were found to leak, so Jabiru rescinded the approval for aircraft but not the engines. This information is now dates, so always be sure to get the latest from the manufacturers of engines and airframes – and do not trust hearsay. But why use an ethanol blend if you can get ethanol-free? It will always contain less energy, reduce maximum power and range, all bad news for aircraft. You can not eliminate the problem of water absorption and phase separation unless you keep the ethanol out in the first place. Far better is to encourage your airport to find a supplier of quality, 91+ AKI, ethanol-free fuel as ~120 airports across the country now do. Contact Mark Ellery at Airworthy Autogas too for help. Urge your favorite aviation alphabet group (LAMA, USUA, EAA, AOPA, GAMA, NATA, NBAA, etc.) to promote the use of mogas as a means to lower the cost of flying and do something real about reducing our lead emissions, a public relations nightmare for pilots and airports.

      • Dietrich Fecht says

        Thanks a lot for the competent advise. When a new plane is built: Is it wise today to build the components of the airframe which come in contact with fuels out of materials which are suitably for fuels with ethanol content and resistant against corrosion originated from alcohol in the fuels? Only to be on the safe side if perhaps some ethanol accidentally gets lost in a normaly ethanol free fuel. Or to be able to fly with street automobile fuel when it makes sense.

        How can we see what components like fuel switches, gaskets, fuelhoses, drain valves, tank assemblies, fuel line connectors a.s.o. are suitable for ethanol? What plastics are resistent? Ethanol reststant automobile tanks usually are made out of plastic. What material is that? What about windshields when fuels are accidently spilled? Is stainless steel 304 or 316 for tanks, fuel lines and connectors a good idea?

        Are suppliers of aircraft parts able to deliver ethanol resistant parts? Or do we have to make them for ourselves or take them from automobile parts suppliers?

        Where we can learn how to build a closed fuel system like at automobiles to prevent against water absorption.

        Yes, auto fuel with ethanol has a little less energy content per weight. But it is much cheaper and always available at millions of street pumps. Only for the case that ethanol free fuel is not available and a replacement for leaded fuel struggles to become reality.

        • Kent Misegades says


          The problem here is that no one knows how much ethanol will be in our fuel tomorrow. The EISA 2007 RFS ethanol production mandates that have adulterated our gasoline with ethanol is aimed at taking all fuel to E85, 85% ethanol. E10 is only an early step along the way. It is hard enough to protect an open-vented fuel system for E10, but who knows what will be needed for E20-E85? The auto companies deal with this now, and clearly the Flex Fuel E85 cars can handle this. But they have closed fuel systems, fuel in the car’s tank is replaced nearly weekly (not parked in a hangar 99% of the time) and most owners keep their cars only 5-10 years versus aircraft. The best way to deal with ethanol is keep it out of fuel – since ethanol may not be pumped in gasoline pipelines, it is readily available at fuel terminals around the country where it is first blended with ethanol.

Leave a Reply

Your email address will not be published. Required fields are marked *