Shell Is Saying The Right Things About Unleaded Avgas

Shell’s announcement that it has an unleaded avgas formula that is working well at a full 100 octane caused a commotion this week. It’s the first time any major oil company has said it has a solution to the lead problem. And a company the size of Shell brings credibility to the effort to transition to lead-free avgas.

I had a chance to speak with Michael Sargeant who is Shell’s Avgas Commercialization Manager. Michael’s title fully describes the hard part of the conversion to unleaded avgas which is to get a fuel out of the laboratory and into airplane fuel tanks.

Shell has been working on a 100LL replacement for the past 10 years and recently began engine testing with Lycoming and flight testing with Piper. Though Shell is tightlipped about its lead-free avgas formula it would be a safe guess that the company’s development of 100 octane plus auto racing fuel contributed to the new aviation fuel creation. Most of the development work was done at Shell labs in the UK.

Here are the headline concerns we all have for the unleaded replacement fuel and I asked Shell’s Sargeant about them:

Full 100 octane performance: Shell is convinced that its new fuel formula will provide the same or better octane performance as 100LL. That means all piston airplanes that require 100 octane can potentially use the new fuel without performance loses.

Compatibility with 100LL. Any unleaded avgas will be phased into the fuel distribution system so for a long time we will fly with a mixture of the new fuel and 100LL in our tanks depending on where we fueled last. Sargeant says Shell’s testing shows the unleaded fuel mixes with 100LL successfully.

Compatibility with fuel system materials: Chemicals that boost octane can attack and even dissolve some hoses, sealants and other materials used in an airplane fuel system. Shell has done  testing of its new formula that, so far, shows compatibility of the fuel with popular fuel system materials. Sargeant said Shell has room to “tweak” the fuel formula if further testing shows incompatibility.

Producibility: To be economically effective an unleaded avgas must be producible without big investments in refineries or chemical plants. The market is so small that it would be hard to justify investing millions in new equipment to serve the shrinking avgas market. Shell says its new formula is producible without major investment in existing equipment. Shell will make the fuel formula available to others under licensing or some other agreements so the fuel will not be a regional or single-brand product.

Certification: The quickest path to certifying a new fuel would be to obtain STCs for specific airplane models much as the EAA and others did with autofuel a number of years ago. But that would restrict use of the new fuel to only those models with an STC and would provide virtually no incentive for the national fuel distribution system to stock the new fuel.

The only truly effective certification of a new fuel is to gain fleet wide approval, even if certain modifications, even if only paperwork, are required. Shell says it will seek fleet wide approval instead of STCs in individual airplane models. The first step is to present the new fuel to ASTM, the international body of material standards, which Shell is doing next week. Once an ASTM specification is in place Shell says it will work with the FAA and other aviation certification authorities around the world to gain approval for the new fuel as a 100LL replacement.

How long will it take? Shell’s Sargeant says the company is confident in the performance of the fuel based on the 10 years of development and testing already invested. The hard work ahead is testing the fuel in real airplanes under a variety of conditions to convince regulators the fuel is safe and effective. Sargeant acknowledges there is much to do, but says Shell’s focus now is on the approval process and estimates that if all goes well the new fuel could be in the FBO network within 2 to 3 years.

How much will it cost? Shell’s Sargeant says it’s too early to know precisely what the new unleaded avgas will cost, but says it must be, and will be, competitive with 100LL prices. He said Shell knew from the beginning that a new fuel had to be price competitive and they would not have continued development if they didn’t believe they could achieve that goal.

The bottom line: Shell’s announcement has created a new urgency among fuel producers, fuel distributors and aviation regulators in the drive toward unleaded avgas. When one of the world’s major energy companies says it has an unleaded formula that works, it knows how to make the fuel in necessary volumes, and that the price will be competitive with 100LL all ears perk up. The way I look at it Shell has turned the situation upside down. Suddenly we have gone from a “prove you can do it” stance to a “prove you can’t do it” outlook.

The hard work now moves into endless meetings, actual flight testing, and negotiations with all players involved. We won’t know anything for sure for years even if the new fuel progresses toward certification and delivery as quickly as Shell hopes. But in aviation terms, 2 to 3 years to certify and deliver a new airplane or engine, much less a new fuel, is lightning speed. All we can do now is watch and wait.

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45 Responses to Shell Is Saying The Right Things About Unleaded Avgas

  1. Marc Rodstein says:

    This is good news for aviation in general, but not so good news for the smaller companies that have been working on an Avgas replacement. Will they continue to invest in this area now that they know they will have Shell as a major competitor?

    • Bill P says:

      I agree with the ambivalent feelings. You have to feel for the brave entrepreneurs who have been busting their humps these past years working toward solving this difficult problem, and now a 1000 pound gorilla comes out of the blue with this announcement.

  2. Fred B says:

    This is great news and a big congratulations and thanks should go to Shell Oil! Its a shame that the certification process has to take so long given Shells’ documented 10 years of research and recent practical testing. One has to ask; since Shell is the subject matter experts who have the scientific and empirical data to show to the governing organizations why does it take so long to approve? My only answer is; bureaucracy which is the kind of drag we in aviation cannot over come it seems!!!!

    Thank you Shell Oil for the hard work and perseverance to make this seemingly impossible development a reality!

    • Sarah A says:

      So far it is just a labratory product with only one hour of flight time with certification not even started. To say that burocracy is slowing us up on this 100LL replacement is a bit premature as is the assumption that it is ready for fleetwide use. Compatability with existing fuel system materials is critical and we do not yet know how much testing has been performed. If we switch and aircraft start crashing it will be a bad thing. As much as we hate the bloated burocracy of the FAA it does serve a purpose and they will want to see some significant field testing before a fuel is approved. How much work went into the switch to 100LL which was probably a lot simpler then then the task ahead. The news is great but premature and it would be better if they could say they already have several hundred hours of in flight testing already completed.

  3. Rodney Hall says:

    Yes, I think the bureaucracy is nothing but a burden on any new product. Testing and restesting ad infinitum adds little to the safety or compatability of any product. People will still manage to screw up. There will be some product it is eventually found to be incompatable with on a 1942 Sqeegite that hasn’t had a new hose in 40 years or something and someone will file a lawsuit as a result. I am not really surprised by Shells announcement and frankly I would think it would take less than 10 years to come up with an unleaded fuel if the bureaucratic hurdles weren’t in place and we got some tort reform in this country (or people actually took responsibility for themselves). THis new fuel will have little effect on safety. People will stil run out of gas, end up with water or other contaminants, or let hoses and fittings deteriorate until they fall off. I am glad they may have solved this “problem” but in my view it wouldn’t even be a problem if the government (EPA) minded it’s own business and kept out of ours.

    • Jeff Boatright says:

      Spend a day in any city in China or India, large or small, then get back to me about the EPA.

      Back on point, if FAA wants to see testing done on new fuels to ensure compatibility with the installed fleet, I’m all for it. I’ve gone through just a small fraction of what I thinks it takes to test seasonal mixes of mogas with and without ethanol, and even on my very simple system (C-85 with M-S or Stromberg with gravity feed), there’s lots of factors that I couldn’t control for or anticipate.

      I don’t see how individuals’ taking responsibility for themselves would apply here. Individuals don’t have the resources to properly test even their own systems.

      We could trust the data from the oil companies, but largely what keeps them “honest” is fear of lawsuits (if you think it’s the invisible hand of the market, you haven’t spent enough time with oilmen), so if we toss in “tort reform”, there goes another tool in our toolbox. Regardless, it might do my widow’s bank account a lot of good, but fixing the problem after I’ve crashed and burned isn’t much of a solution for me.

      So what are we left with? Pretty much we’re left with the pre-emptive power of regulation. Hopefully that regulation is based on participation from industry and consumers, with as light a touch as possible from the government. I don’t see a better solution.

  4. Bill Tomlinson says:

    As I understand it (and I shall be the first to concede I may have it wrong) the problem with using mogas in aircraft is that it is more prone to vapour locks under reduced pressure, i.e. at altitude.

    So why not just pressurise the fuel system?

    This is so obvious that I am sure the big guys must have thought of it, and there must be a simple explanation. But I should be glad to know what it is.

    • Pressurization of the fuel system is not feasible. Even as little as three PSI amounts to more than 400 pounds of force for every square foot of fuel tank surface doing it’s best to rupture the tank. At 10,000 feet the difference to sea level pressure is greater than 4 PSI.

      • Bill Tomlinson says:

        Thanks for your reply. But I am not convinced.

        If you have a flat tyre on your car it takes about 8 psi just to get the rim to lift slightly. That should be enough to bring you back to sea-level pressure at 10,000 feet.

        The old (rear-engine) VW Beetle had a pressurised tank for its windscreen-washer liquid. There was a tyre-valve next to the filler cap; once you had put water, plus additive if required, into this tank you would screw on the cap and then inflate the tank to 20psi. It was a light plastic container, similar to a plastic milk bottle.

        • Boscoe says:

          A tire is designed to withstand a pressure differential of 8 psi. Actually, a pressure differential of much, much more than that.

          A fuel tank is not designed to withstand much, if any, pressure differential. It is vented to the atmosphere.

          Pressurizing a tire or a small vessel is not problematic. Pressurize a large volume tank with a surface area of hundreds, if not thousands, of square inches, to just several psi, and the loads on the tank are substantial.

          Many, many years ago someone at the factory forgot to remove the fuel vent outlet cover on an L1011 Tristar. Just a cover. You would think that a psi or so would blow it off. Unfortunately, before that happened the wing inflated. Can you say remove and replace the entire wing?

      • pete says:

        Boy am I having trouble with the thinking . . 3 or 4 psi is just that. Three or four lbs. per square inch. One does NOT total up the number of sq. inches. A thank / system would have 3 – 4 psi ONLY, no matter where you checked the pressure.

  5. Jeff Boatright says:

    Possibly good news or possibly FUD. So far we have one press announcement and a few statements from three PR spokesmen. By definition, “saying the right things” are what people in those positions are paid to do. ;)

    That said, if this is the same as or is based on Shell’s URT Advanced 110 octane racing fuel, then there could be even more benefits to the GA market than what I’ve so far seen discussed in aviation circles.

    For instance, the smaller engines in the GA fleet that don’t need the higher octane of 100LL probably are producing less torque (due to the slower burn rate when burning avgas) than they did when those engines were first developed and 80 octane was the fuel of choice. From my brief reading on Shell URT, detonation elimination is obtained differently than just changing the burn rate, so our smaller engines could potentially provide more torque (= more thrust from prop).

    The only drawbacks I’ve found are that currently Shell URT costs >$10/gal and (I think) it weighs about 14% more than avgas. Not insignificant.

    I found several discussions about Shell URT Advanced racing fuel at motorhead websites. This one was especially interesting to me as presents some real-world testing by consumers:

  6. Nigel Hitchman says:

    Good news that Shell is doing this and that it meets the full 100 Octane required by some engines.
    However unleaded Avgas is already available in the form of Total 91UL, which is now sold at quite a few airfields in Europe. I understand this is basically 100LL without the lead. This has been approved by engine manufacturers for quite a lot of current engines including Lycoming O-320 and O-360 even the higher compression models. Obviously not 100 Octane, but it has proven enough for a large percentage of the GA fleet over here. It is approx. the same price or slightly less than 100LL (although that is twice as much in Europe as the US)
    There is also a locally produced 96UL fuel that has been available in Sweden for many years and is approved for many engines.

  7. Mark Navratil says:

    Mac, one question I was hoping you would ask is about long term stability of the fuel. 100LL can be stored for many years and still be safe to use. Many other fuels including what we put in our cars can start creating problems after only a few months if it’s just sitting in the tanks. I recall talking to the guys at the Swift fuels booth at Oshkosh a couple years ago and I don’t remember the details but there was some aspect of the fuel that would degrade with time (I think the proposed solution was an additive to restore it to it’s full performance spec). It would be interesting to know if Shell considers their formula to be on par with 100LL in this regard.

    • Mac says:

      Hi Mark,
      Storage life, or stability as you note, is a spec of 100LL. Shell plans to come as close as possible to matching the stability of 100LL. Will they be successful? I hope so.
      Mac Mc

  8. DEL says:

    “Shell’s Sargeant says … the new unleaded avgas … must be, and will be, competitive with 100LL…” But that’s not the right competition. As long as there’s no competing commercial product other than Shell’s, and if unleaded avgas becomes mandatory, Shell will be able to charge as much as they fancy.

  9. Boscoe says:

    What does competitively priced mean? Same price as existing 100LL? Current price of 100LL plus X? Current price of 100LL plus X plus Y?

    What does competitively priced have to do with it anyway? When 100LL is phased out, will the price of 100NL (no lead) really matter?

    What is a gallon of water worth if you have to have it and the supply is limited?

  10. Steve Sokol says:

    This is good news, but I still see it solves the wrong problem. The new unleaded fuel will remove TEL – excellent and long over due – but face it: this is a PR issue. Given the amount of general aviating that goes on these days, lead emissions are not much of a threat to the public.

    The real problem with avgas is the price. And it is extremely unlikely that Shell will be selling their new unleaded fuel below the current market rate for 100LL – roughly $6 per gallon. And at $6 per gallon, the GA piston market isn’t going to improve.

    The real solution – the one that gets more people into flying and lets us spend more time in the air – is to move the piston fleet to auto gas. Here in Kansas City you can buy 87 octane (unfortunately with ethanol) for $2.78. Imagine how much more you could fly at that price.

    A surprisingly large number of low compression aircraft engines can already run auto gas without modification. It is utterly ridiculous that Lycoming and TCM don’t sell those engines pre-approved for mogas. They’ve surely already done the testing. If not, they could probably buy out Petersen Aviation or make some kind of deal with the EAA – both of which have mogas STCs for their engines. Either, this would take care of a very large portion of the piston fleet.

    From what I have read, those engines that cannot transparently run mogas are generally high compression and/or turbocharged. These require the higher octane level of 100LL to prevent detonation – the lead content is immaterial. Even these can probably be retrofitted to burn mogas. These engines tend to be installed in larger, more powerful and more expensive aircraft – the kind owned by folks who probably don’t notice the bite of $6 / gallon fuel.

    The biggest drawbacks to mogas for most of us is availability. If more of us paid the paltry fees for the STCs and demanded it from our FBOs, this problem would probably take care of itself.

  11. Richard Sweet says:

    Isn’t the effect of unleaded gas on valves and seats pretty important? Maybe all engines without hardened seats and valves will have to have those components or even the heads changed in order to work with modern fuels.

  12. Alex Kovnat says:

    Last Monday evening (12/04/2013) I was at an annual dinner put on by a flying club not far from me. I was sitting across from an owner/pilot whose aircraft, a Diamond DA-20, consumes ~5 gallons/hr and can attain a true air speed as high as 138 knots. Compare that to the Piper J3C-65, whose fuel burn is similar but whose top air speed is ~75 knots. And also, the DA-20 has a lot more range.

    My enthusiasm for all this aviation progress cooled a little though, when I thought about it and realized that the DA-20 (like many other piston aircraft) requires 100LL while the Cub’s 65 HP Continental engine is happy with 80/87 octane avgas.

    Since the reason we want totally lead-free 100 octane avgas is elimination of lead pollution, there are things we can do right now while waiting for Shell’s lead free 100 octane avgas. Frank Robinson made a great decision when he introduced the turbine-powered R-66, which (like all turbine aircraft) doesn’t need no steeenkin’ lead, as does the piston-powered R-44. If 100LL is that bad for the environment, we can expect more aircraft, rotary and fixed wing, to use turbine engines. Numerous Cessna 210′s have been converted to turbine power, and a while back an aftermarket aircraft modifier developed a turbine retrofit for the Beechcraft Baron. And there are turbine Bonanzas out there.

    We can also consider using 93 octane autogas (i.e. Shell V-Power) as much as possible. What effect will it have on the performance of aircraft like the Cessna 172 or Piper PA-28 aircraft often used for training new pilots? Perhaps such aircraft could use Shell V-Power (or equivalent) for basic flight training, where one doesn’t have to fly very high nor fast, nor carry much payload.

    A Chinese aviation firm has developed an all-electric aircraft. Since aircraft flown strictly for the joy of being airborne or for basic flight training don’t need to go very fast nor far, one hopes we’ll see more of those in said roles.

    Another possibility is E-85 fuel. Years ago I saw aircraft modified to run on straight ethanol at AirVenture Oshkosh. A professor at Baylor University carried out considerable research on ethanol as aircraft fuel. Ethanol suffers the disadvantage of having only 63% of the energy content of gasoline but again, if you’re using an airplane mainly for fun or flight training, this won’t be too much of a problem.

    Even today, with 100LL amounting to only a small percentage of liquid fuel consumption and with lead gone from house paints and motor gasoline, almost all lead exposure is from legacy sources such as homes in slum areas built before lead paints were outlawed. Perhaps the real crisis of our time is intellectuals who never liked automobiles nor general aviation aircraft anyway.

  13. John Lotzer says:

    Excellent follow-up questions Mac!
    This announcement by Shell is very encouraging in an otherwise subdued market. Piston A/C sales, FBO fuel sales volumes, student starts (and finishes), general aviation service profitability have all been depressed by the threat of EPA action against 100LL. FBO’s and small airports are closing as there are declining numbers and fewer profitable opportunities for the “non-jet center” type of operation.
    While Shell’s unleaded product is very much needed it should be remembered that it is a replacement of a currently available product and it will not solve general aviation’s issue of declining numbers.
    As an industry we need to look at the government oversite issues? Every time there is an accident there are numerous government agencies involved and they always lead to more regulation. I have been flying professionally for 40+ years and I can’t believe the level of oversite and regulation every new pilot is subjected to. Beginner pilots and CFI’s used to have to overcome fear of flying, but now they have to overcome fear of prosecution. Too much fear; too little fun leads to further decline in active pilots.

    So, kudos to Shell, but there continues to be other issues to consider to get some growth into the aviation industry.

    John Lotzer

  14. Al Gibbs says:

    I own a Rotax-powered Diamond DA20. Both Rotax and Diamond have said it can run on MoGas, but I have had trouble getting the engine started in tests with fresh E10 in the tank. Lead is particularly bad for this little engine and the potential for lead fouling requires some extra care with 25-hr oil changes if you want to keep your bird out of the shop. Thanks to political meddling, getting unleaded fuel without E10 has been a real challenge for pilots in California. I can hardly wait to start putting this fuel in my tank.

  15. Bill Tomlinson says:

    I recall a long time ago (from memory it was in “Flying” magazine in the 1970s) reading of an experiment in which a Beech Musketeer was converted to run on propane. [For those under the age of 50, who have never heard of a Musketeer, it was rather like a Cherokee, but double the price – and similarly powered by a Lycoming O-320].

    Does anybody know what the outcome of this experiment was? Sounds like it could be the answer to our prayers. Especially as propane is so much cheaper than even mogas, never mind mogas, at least on my (east) side of the Atlantic.

    • Mac says:

      Hi Bill,
      I do remember the experiment. Those of us in the major aviation media went out and flew the Musketeer. It was a methane gas compressed to liquid. At the time Beech was big into cyrogenics, mostly for use in target drones that it built for the military. The Musketeer flew ok, but down a little on power compared to avgas. It took about 30 seconds for some wag to call it the fart flyer.
      Mac Mc

  16. Alex Kovnat says:

    Propane has its good points. Years ago, the Chicago Transit Authority had a fleet of Faegol Twin Coach transit buses powered by Hall-Scott propane engines. They (and also the CTA’s fleet of trolley coaches) were replaced by Diesel buses. But nowadays, we have strict exhaust emission standards which are a problem for Diesel engines. We also have more efficient propane engines, using the liquid injection principle. So propane is a viable option for transit coaches, school buses, pickup trucks, and other vehicles. See

    But aircraft? Unfortunately propane, while it doesn’t have to be stored under as high a pressure as compressed natural gas (3600 psi) or hydrogen (5000 psi or more), the pressure that propane exerts on storage tanks would be a problem with aircraft.

    If anybody can come up with an aircraft certified as Experimental (Part 23 certification would be difficult) running on propane, it would be interesting to see what its performace would be in comparison to the same aircraft with a 100LL-burning engine.

    • Bill Tomlinson says:

      The pressure would simply mean a strong enough tank. According to the FAA a passenger weighs 175 lbs, and the propane tank in my RV is nowhere near that heavy. I should gladly forego one passenger in exchange for getting my fuel for less than a quarter the price of avgas!

      • Reid Sayre says:

        Let’s think about propane tanks for a minute.

        It happens I have an empty tank and a full tank for my grill. The difference in weight between those two tanks is about 14 pounds. The energy per unit weight for propane is about the same as gasoline. So one barbecue grill propane tank has about the same energy as a little more than two gallons of gasoline.

        But the empty propane tank weighs 19 pounds! Now granted that might be overkill. If there are any propane tank engineers out there, how about a quick design for a 20-gallon propane tank (one for each wing) that would fit in a wing? And what might those tanks weigh (and remember you need two of them, and the wing might need to be strengthened), and what might they cost to manufacture?

        Of course, one could always put a tank in the fuselage, but 240 pounds of propane plus the weight of the tank to hold that much would probably put the CG too far back. You could design a new plane that would work, but converting a 172 probably would not.

        Of course, for a training/fun airplane, you might not need the equivalent of 40 gallons of gasoline. I have based this discussion on my 172 used for traveling.

        Finally, while the energy per unit weight of propane is about the same as gasoline, the energy per unit volume is smaller for propane. The energy in 40 gallons of gasoline takes as much space as about 50 gallons of propane.

        I am not trying to stifle innovation here. I think it’s an interesting idea. But let’s try to keep the whole picture in focus.

        • Bill Tomlinson says:

          Propane liquefies at around 80psi at standard room temperaure. That’s about the same as the pressure in the tyres of a medium-sized truck. Do we really need these heavy steel tanks for 80psi?

  17. Josh says:

    I chuckle a bit when Shell says there usually is a modest increase in cost when moving to unleaded fuels – kind of like when the doctor says you might feel a little prick! I really see this as a balance of cost vs reward. All the talk about propane, methane and such is interesting, but it would be far easier to convert the 100 octane fleet to run on 92UL or something like that. The guys really hanging in the balance are the Bonanza/Baron, Cessna 210, Piper Saratogas & such. My best guess is that this segment will be either faced with 100UL that costs between .50 & $1 per gallon more than today’s 100LL, or modifying their aircraft – neither seem to be a good option, although it seems to me that the payoff for converting an aircraft to run on 92UL would be a better deal over the medium to long term for these owners. $8 – $17 per hour increased fuel cost on an IO-550 Bonanza adds up pretty fast – even faster on a twin. Regarding larger aircraft, I feel like the piston cabin class twin’s days are numbered in the corporate world – not because of the demise of 100LL, but simply that insurance companies won’t write adequate per passenger limits on insurance unless you’re at least a turboprop. I have a client now that operates a 421 who is looking at a King Air for this very reason.

    • Alex Kovnat says:

      This past year or so, there was mention in an aviation magazine or two about 421 airframes being converted to turbine power. Hope it works out!

      • Bill Tomlinson says:

        There are a number of good turbine conversions around. But they are NOT cheap!

        • Josh Johnson says:

          Bill, you’re absolutely right, there are no cheap turbine conversions, not at least until you amortize the costs out over several thousand hours – which works for the corporate operators. The real question is for the high performance piston operators, do they save .50/gallon and modify their engines to run 92ul or do they spend an extra $1 per gallon to get 100ul.

  18. I fly a rotax 2 stroke and I would love to have unleaded as an option at the airport instead of bringing in mogas with menthonal in from the local gas station. Yes I know rotax says I can use 100LL, but I am also told by other two stroke flyers that the 100LL tends to foul the plugs. So far 3 years on unleaded mogas and no problems, so I will be happy when I can get unleaded at the airport and not have to haul it in. At the moment I plan all my flying so that I never have to refuel away from home.

    Unleaded at airports would make me happier about trips where I might have to refuel enroute.


  19. Dennis says:

    There is a lot of discussion about options for a portion of the fleet. But if we don’t come up with an option that everyone uses, there won’t be enough volume to make a higher octane option economical. We need one standard fuel that everyone can and will use, in order to support our aviation infrastructure, and hope for reasonable price points.

    • Steve Sokol says:

      Dennis, I have to disagree. It would be nice if there was a single solution that took care of the lead issue, was a drop-in replacement for 100LL and was economically viable for everyone, but I don’t see that happening in the real world. A two fuel model which includes ordinary auto fuel for those who can use it and a (probably much more expensive) 100LL replacement for those who cannot seems more realistic.

      The recent Red Bird Aviation experiment ($1 avgas) showed that the gating factor in aviation is overwhelmingly the price of fuel. If the only option is the $6/gal drop-in from Shell, the GA market will continue to fade. The best hope is to move the fleet away from specialty fuels and towards commodity fuels.

  20. Bill Tomlinson says:

    Just another maverick thought: what about pure octane produced by the Fischer-Tropsch process? (Or similar.) This is already commercially available though not, I think, in the USA. Would pure octane have a problem with causing vapour locks?

  21. Mike Berg says:

    I flew my Cherokee 140 (0320) on auto fuel for 25 years with zero problems. It would get an occasional drink of 100LL every now and then and I’ve since sold it but the present owner is still using auto fuel and the engine probably has upwards of 1500 hours since overhaul on it. Also, owned a Champ with a A65 that ran on auto fuel just fine. Right now I have a L16 with a 0200 conversion and I’m running a mix of 100LL and auto fuel mostly because of low hours on a new engine. I guess my point is that auto fuel seems to work just fine in low compression engines and mixing isn’t a problem either. Running on 100LL exclusively would tend to foul the plugs pretty bad on the Lycoming 0320 which I thought was a bit of a safety hazard. The Continentals don’t seem to mind what they have in them. High compression engines are probably another story. To me dropping the lead out of the fuel is one of the reasons why auto engines last so much longer now as lead seems to be a contaminate and contributes to engine wear. As a old mechanic I used to spend a lot of time cleaning lead deposits off pistons and combusion chambers with a drill and wire brush (not to mention breathing the nasty stuff). The spark plugs were always full of lead deposits and now with auto fuel take very little cleaning. In fact, spark plugs hardly ever need to be changed any more on any engine that uses auto fuel. Can’t remember the last time I changed them in either my car or truck (or the plane for that matter).

    • DEL says:

      The FAA, with all its bureaucratic heavy machinery supposed to provide for better flight safety, seems to achieve the opposite: auto engines with mogas more reliable than aviation engines with avgas. (That they excel at spoiling the fun and affordability of flight goes without saying.)

      • Steve Sokol says:

        Yes, but… The problem with the FAA isn’t that they hate GA and take joy in forcing us to fly with antiquated gear. The problem is that some combination of congress and the plaintiff’s bar have pinned them into a corner. Their mandate used to be safety and advocacy. Today it is purely safety. Our litigious, risk-averse society has little room for inherently dangerous activities, which includes flying little airplanes. The policies set by the FAA simply reflect that attitude.

        I’ve met a number of people from the Small Airplane Directorate – the FAA group that governs GA. Many of them are pilots. All of them are strong advocates for GA. All of them wish things were different. The upcoming rewrite of Part 23 and Part 21 are steps in the right direction. The new performance-based regulations and the move to consensus standards for compliance will make it easier for manufacturers to innovate. It won’t happen overnight, but change is coming.

        • DEL says:

          I would agree with you they are not GA haters. But as soon as you cast a system in a form of a rigid, encyclopedia-size, FAR, and exorcise common sense and discretion, that result is inevitable.

  22. John Worsley says:

    My IO-540 probably wouldn’t like mogas, and I have my doubts, too. I’m surprised to see only one comment about storage life of mogas, particularly given how much a lot of our aircraft sit. Even though I fly frequently, having four tanks would be a problem. I seldom take trips that require burning the tip tanks, which the manual says should be burned last and filled first. This means low turnover in the tips, or flying with reduced fuel.

  23. Bill Tomlinson says:

    I think if I were buying a new aircraft in the O-320 or O-360 size range I should go for a diesel option, which would sidestep the problem. The bigger guys will just have to bite the financial bullet and go for turbines.

    That leaves the owners of existing aircraft. It would be very painful to have to throw out a perfectly good spark-ignition recip, and replace it with a diesel or turbine costing many thousands, just to appease the Greens.

  24. Mallory says:

    From here it is subjected to maceration by shredding, with the resultant slurry being reduced to
    12mm pieces as per EU Regulations, but also to aid degradation.

    Repeatedly, such wanna be solutions failed to live up to the
    hype. Synthetic blend is not as good as full synthetic, and it is marketed to people that
    can not decide which type of oil to choose.

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