There you go again

On Jan. 19 your bloggers posted a rebuttal to an article in EAA’s Sport Aviation titled “Avfuel Takes on Fuel Challenges” by J. Mac McClellan that deals with the never-ending saga of a replacement for leaded avgas. We did our best to correct the fallacies in the article. Judging from the numerous positive comments we received, most of you agree with the facts that we presented.

In the immortal words of then-candidate Ronald Reagan during the 1980 debate with president Carter, “There you go again.” Incredibly, the February issue of Sport Aviation included a new article (“Fueling the Future of GA” on page 10) that contained even more misleading statements on aviation fuel that demand correction.

First, the author appears to have misunderstood the goal of Airworthy Autogas. This new company is not focused on the fuel that was tested and approved via EAA’s autogas STCs, but rather the automotive fuel that Lycoming specifies in Table 2 of its Service Instructions 1070S. Lycoming calls for an AKI of 93 and a vapor pressure (RVP) of no more than 9.0. (None of the EAA’s auto fuel STCs require an RVP as low as 9.0 and they do not call for more than 87 AKI .) Note too that the 1070S document makes no mention of an aviation-specific fuel in Table 2, since automotive fuel worldwide must already meet ASTM D-4814 or EN 228:2008(E).

Petersen Aviation continued testing on higher compression engines that may operate on 91AKI autogas and has numerous STCs to show for it, including those for the Beech Baron and Cessna 210. This is significant because it proves that auto fuel need not only be used in the realm of J-3s and Cessna 150s, but could also be used in larger, modern high-powered airplanes.

Second, the article suggests that auto fuel has changed greatly over the past 30 years, “and sometimes not for the better.”

Not for the better insofar as ethanol is concerned, indeed that is true.

Fortunately there are simple tests that anyone can perform to determine the presence of ethanol, so the chance of its use by mistake is miniscule.

Furthermore, airports that sell auto fuel do not purchase it from local gas stations, but from terminals before ethanol is added. Still, those who self-fuel have more than 7,700 gas stations to choose from where ethanol-free (E0) is sold, which can be easily found at (I have its free app on my iPad to help me find E0 for my cars, the fuel I prefer).

The prevalence of ethanol in gasoline is the only downside (significant though it may be) to making use of an auto fuel STC — but remember that airports do not buy their fuel at a gas station. Aside from the ethanol, auto fuel is cleaner than it ever was and has a lower vapor pressure than it ever did. Indeed this makes it more like aviation fuel than ever. So to imply that today’s auto fuel is somehow out of spec or unusable is a complete falsehood.

We welcome Lycoming’s work toward its 93AKI auto fuel because it vindicates the basic chemistry of the fuel. Lycoming would not be approving auto fuel if there were issues with it. Nor would Continental, Rotax, ULPower, Jabiru, D-Motor, AeroVee, Viking and nearly every other aviation piston-engine manufacturer that now type certificates their engines for auto fuel.

Finally, in the fourth paragraph of the article the statement is made that an unleaded replacement for 100LL must be producible in large quantities, distributed throughout the nation with a whole new infrastructure, and should be economical enough not to deter flying. There is only one fuel that meets those requirements today and that is likely to continue to do so in the years to come, and that is 91AKI automotive gasoline, supplied today to more than 100,000 gas stations in the US through a vast network of highly-competitive, independent fuel distributors.

The argument that FBOs cannot afford an additional fuel tank for mogas is a red herring too — modest self-service fuel systems cost less than $40,000 and pay for themselves in a few years. Small airports across the country are adding self-service Jet-A fuel systems, not because turbine aircraft are based there, but speculating that they might be one day if the fuel existed. Why not do the same for mogas and get people flying again who can not afford $8 avgas? Many small airports these days manage to find the funding for palatial terminals with rarely-used meeting rooms comparable to Wall Street board rooms  — funding is clearly there for those who seek it.

Lastly, the EAA article repeats the “70/30 mantra”, claiming that a small number (less that 20%) of aircraft that need 100LL consume most of the fuel sold. Fact is, over 80% of all piston-engine aircraft today can operate safely and legally on mogas, as shown in our study from 2012.

In Europe, where poor weather restricts GA flying for half of the year, mogas is widely available at airports and has been reported as constituting over 50% of all fuel sold for piston aircraft. Why is it impossible to do the same in the U.S. with its larger pilot community?

And what about those high-performance, 100LL-burning aircraft? Using the same water/methanol injection system that has been approved by the FAA and in use since 1989 on 210s and Barons (INPULSE), the remaining 20% of our GA fleet could be converted to 91AKI auto gas if only the alphabets would get on board. This is not likely though since the people involved with the selection process have all voiced their support for a 100 octane solution only and refuse to consider anything else. This is unfortunate given that we’ve had the solution right in front of us for over 30 years.

Whatever fuel prevails through the selection process set up by the FAA, let’s hope it’s priced less than what we’re paying today for avgas. Too many people are dropping out because they cannot afford 100LL and now with ethanol prevalent, those who self-fuel have difficulty finding aviation-grade auto fuel at gas stations.

Insisting on 100 octane means the cost of production will be much higher than it would be for a 91 or 93AKI. If the new fuel cannot be made less expensive than today’s 100LL, then eventually only the very wealthy will be able to afford to fly.


  1. Bob Parry says

    I agree with most everything that Ken said in his article. If installing a water/methanol injection system allow the use in every engine than this should be done ASAP. It is however a stop gap measure. “Modern” aircraft piston engines have to be updated. Using 70 year old point triggered fixed timing magneto ignition will have to be updated.

    Modern automotive engine have compression ratios as high as 11:1 and run higher cylinder pressures and still avoid detonation. These engines also are nearly pollution free (CO2 not withstanding). Not all of the tricks in auto engine should be used in aircraft, such as active valve timing. I think that is not necessary for an aircraft engine and although very dependable in cars would be a bit risky in aircraft. Electronic ignition and injection certainly, with separate backup systems or redundancy would be more dependable than existing systems.

    A deadline for the implementation of unleaded fuels is absolutely required or another 40 years will pass before anyone does anything. We did not get the engines in modern autos from free market competition, we got them because they were told to things better and they did. Better than we could have dreamed of in the 1970’s when this came to a head in the automotive industry.

  2. Joseph says

    One other thought if the E0 was offered at the airport situated so that they could sell both to airplanes and to the public it would be one more source for those that seek out pure gas for their cars, boats, and lawn mowers. Who knows may even attract someone to swing by the flight school while they are there.

  3. Rich Bettencourt says

    Kent I just LOVE it when you tear into these people! As far as Macs articles,unless you do not have two engines and your not hard IFR you ain’t havering fun,that’s why I do not subscribe to Flying magazine.

  4. brett hawkins says

    I fly a 2-seat experimental and follow the articles posted on the EAA website (including Mac’s Left Seat blog). Mac states that he flys a Baron, and he has recently come under criticism by some of his readers for his propensity to focus on fuel and IFR gadgets for those flying light twins and heavier aircraft on business missions (as opposed to the primarily recreational activities of most EAA’ers).

    I have put thousands of gallons of regular mogas through my O-320E2D without a hickup or burp. My composite wing tank has never leaked, no O-rings have dissolved, and when my engine went to a major shop in the Rockies for an overhaul 6 years ago there were no comments whatsoever about the type of fuel used in that engine. I am a fair weather flyer and rarely exceed 10,000ft, so maybe I have not put that cheap gas to a real test. However, it has worked for me and saved me thousands of dollars in operating expenses.

    A few years ago I moved to a rural area where pure (no-alcohol) unleaded premium is always available, and now run my cars and aircraft exclusively on that fuel. It is slightly more expensive than E10 regular but still much cheaper than AVGAS. I pay for it simply because I want to send a message to the EPA and the ethanol industry by supporting businesses that offer pure gas.

  5. Art says

    I seriously question these statements about the “few airplanes that require 100LL.” There are more than you think. Lycoming created the 200 HP angle valve 360 series by increasing the compression ratio. Guess what? Higher compression ratio, higher octane. Yes, I can burn 91 octane, however Lycoming representatives stated that I cannot let my manifold pressure exceed 19 inches. So these “few airplanes that need 93 octane) include the 200 HP Arrows, Mooneys, Cessna’s (especially the Cardinal RGs). Changing to diesels in these airplanes is very difficult, as they are all tightly cowled. Arrows have interference with nose wheel, Mooneys are just tightly cowled. So for us, without a source of 93 aviation grade gas, owners of 200 HP Lycoming aircraft may be donating to the beer can manufacturors.

    • Nathanael says

      But 93 is easy enough to get. E0 at 93 octane is made for premium automobiles, and is VERY common — picking a completely random location on, I find 93 octane. Even 95 is available.

      It’s only the insistence on 100 which causes trouble. How many planes need more than 95 octane?!?

  6. Kent misegades says

    Over 80% of the current US piston engine fleet can operate today on mogas through an STC. In most cases the STC requires no modifications and costs a few hundred dollars. If one does the math on a Baron flown 200 hours annually, the time to payoff the INPULSE mod is less than two years. The greater the spread in Avgas vs Mogas prices, the quicker the payoff. The alternative, waiting even longer for 100UL, which will not be any cheaper than Avgas, will only drive more airports to ruin, force closure of more maintenance shops and schools, and drive more pilots to hang up their wings for good. Boats are cheaper, great fun, and barely regulated.

  7. Norman D. says

    I wonder how one convinces airport managers and airport boards to install Mogas facilities. when the response is “Chicken Little” or “Oh the liability insurance goes sky high!”

    I spend my winters in Florida and summers in Michigan. I have yet to find a Florida airport selling Mogas. The response I get from airport managers when inquiring about the absence of Mogas is a blank stare and “It’s too expensive!”

    My airport in Michigan (RMY) has been selling Mogas quite successfully for several years. The city airport board and former airport manager were obviously enlightened individuals who were able to supply a need to the flying public. I used the Mogas exclusively in my Cessna 120 and other than the unpleasant odor, it performed well in the aircraft. In Florida to get “non alcoholic” gasoline, one must purchase from a marine fuel dealer or a few select Sunoco stations. Fortunately I have one of the latter close by.

    So I wish I had the answer to the complacency and reluctance of airport officials to see into the future and accommodate the majority of pilots and their aircraft. Probably a “good old boys” network of some sort.

    I’m quite dis

  8. says

    I see a now repeated statement that refers to Europe stating that Mogas accounts for 50% of the fuel sold and somehow this is attributed to supposedly bad weather restricting flying activities for half of the year?! The single and only reason AVGAS doesn’t sell in reasonable quantities in Europe is that General Aviation aircraft with WWII engine technology (the average AVGAS bomber is powered by this technology) are pretty much reserved for the richest and most beautiful and hence pretty much on their way out. Conversions are not yet reasonably priced, so many airframes attached to these noise and dirt accelerators are chucked in the process. People are downgrading to save operational expenses.

    General Aviation in Europe is in the beginning stages of what could be considered a recovery from a systematic EASA/ Regulation/ Taxation destruction attack that has forced most operators and owners (less private ownership, more clubs) either out of business or into finding more efficiently running engine technology for its aging fleet of aircraft. AVGAS, as of this writing, costs no less than E2.78 per liter (3.89 of those make a gallon) converting to no less than $14.97 per gallon at my foreign home airport. AVGAS is highly taxed and due to the lead any operator using this fuel (really abolished from automotive engines in the 1990’s) is being punished. At that price, adding landing fees and up to 20% VAT on everything else, one may wish for a bad weather season – the average general aviation pilot will need money falling from the sky to operate a stinky little 172. Filling up our Cessna 414 with 200 Gallons of AVGAS is a ~ $1300 dollar pop here in the U.S. – at my home airport in Europe you’ll do it for a bargain of $2,994.

    We either need engine conversion technology that enables us to convert or operate the fuel-hog Lyco or Conti inefficiency wonders to accept ethanol autogas or we need to invest into breathing new life into diesel & autogas based engines. Who on gods increasingly green earth can afford to keep the mixture rich to “cool” the engine?

    This requires a change in our current destructive and damaging regulatory environment and to stop singing the song that only AVGAS powered engines are the real thing. At the current rate, we’re destined to buy this kind of technology from the big China Man before too long – our industry seems terribly busy selling its brain and power for peanuts.

    My ultimate question in all of this is why our government can fly highly efficient engines in spy drones monitoring the citizens every move and do so without regulatory idiocy and hassle, then why can’t we? Pipers revelation of the Diesel Archer will be a welcome act in Europe and many of us are hoping for the best. Time will tell if conversions to this kind of engine will be somewhat affordable for owners of Archers powered by the current wheeze, squeeze and bang put put puts. We’re 20 years behind the ball with this stuff and operating general aviation aircraft on the same fuel as Joe Blow operates his truck or SUV will be a welcome point for advocacy issues stemming from our list of enemies in the environmentalist arena. To me it seems as if making fuel to accommodate outdated and inefficient technology is like buying a horse that fits the saddle. Good luck, though!

    • Edd Weninger says

      “Who on gods increasingly green earth can afford to keep the mixture rich to “cool” the engine?”

      Nobody. Except for 2 minutes on take-off, I run my IO-520s LOP, a more efficient means of cooling than ROP.

  9. Sam says


    I like your point about airports adding Jet A in anticipation of selling the fuel. Why not Mogas?! At the same time, $40K for a standalone fueling station that can only sell fuel to a limited number of STC’d aircraft that don’t burn much fuel, seems like a hard sell.

    You talk about the INPULSE system. At $12K for a single engine and who knows what the price will be for a twin, I am not sure if this is a viable alternative. Video here:

    Then you have the problem of covering the few aircraft in the fleet that need the lead. Peterson talks about this on his website. Maybe developing a leaded octane booster, like what ASL is working on, is a better way to go instead of ADI.

    As you say, the main thing is cost and Mogas is a great way to get cost down. I just think there are a lot more challenges to consider. The biggest problem, in my limited view, is the cost to switch to Mogas. I hope I am wrong

    • KW says

      A lot of smaller airports have discovered ways to set up fueling for far less than $40K. But your question is easily answered: any airport that wants to buy autogas for $3.50 per gallon and sell it for $4.25 per gallon to pilots who don’t want to spend $7.00 per gallon for 100LL will find it worth the cost.

      • Sam says

        I am curious how they do this?

        I know that you can get a credit card reader for your iphone for about $200, but that means you have to be on site to make the sale. A stand alone credit card system will cost $7K+. Is there any way to get around the expense of a tank?

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