Seriously? Another unleaded avgas thread . . . ?

[A64Pilot]

The whole Diesel thing just doesn’t make sense to me, it’s actually pretty easy to build a gasoline engine burning auto fuel that makes WAY more power than 200 HP. The secret is in a Modern four valve head and combustion chamber, sure that takes liquid cooled heads, but even Rotax can do that, it’s not hard.

Dodge has an engine that makes over 1,000 HP on E-85, and it even passes emissions.

I bet lunch you could easily make our 200 HP Lycomings run just fine on E-85, Lycoming has an IO-540 Certified and running in Brazil on pure Ethanol, has for years.

Fuel burn would go up with E-85, how much? Maybe not a whole lot who knows?

My guess is the way to go might be build an Experimental engine that once well proven etc then you Certify it.

[Pinecone]

23 hours ago, Echo said:

UL94.  I am in.  Ditch the lead.  Same infrastructure.  No STC.  Lower fuel costs.  DO THIS!

Can you burn UL94?  I can't.  Edit, nope, M20E is not listed on the Swift site.  So great, the world does to UL94 and your airplane is now worthless and not flyable.

Most 200 HP IO-360s can't.  My 180 hp AEIO-360 on my other airplane was originally certified for 91/96, so can.

 

[Chris K]

GAMI received an STC by the FAA a while back and already being sold at a handful of airports.  Swift for only certain engines, and VP racing in the process of testing.  So far the only complaints on the GAMI I've heard about were via Cirrus owners (fuel leakage through seals/gas tanks).  To the OP, it's easier to test and switch the fuel being used than an entire GA fleet of engines.  Are some of the technologies outdated?  Without a doubt considering how far ahead the auto industry has come vs aviation in terms of efficiency and power output from new technologies.  Part of the problem is government certification requirements.  With computer modeling and other streamlined testing methods available today, the entire process is in dire need to be revamped. Surely if costs of testing and certifying engines for existing aircraft were reduced, there likely would be newer/modern engines available to consider as replacement when TBO rolls around.

Separately, wondering if anyone in the Mooney community has tried any of the new fuels yet?

[IvanP]

1 hour ago, Chris K said:

 

Separately, wondering if anyone in the Mooney community has tried any of the new fuels yet?

Check the General Mooney Talk forum. Very long thread on G100UL

[EricJ]

2 hours ago, Chris K said:

So far the only complaints on the GAMI I've heard about were via Cirrus owners (fuel leakage through seals/gas tanks). 

...

Separately, wondering if anyone in the Mooney community has tried any of the new fuels yet?

Yeah, you really need to get caught up via the thread on G100UL.

[A64Pilot]

On 2/5/2025 at 9:33 AM, Pinecone said:

Can you burn UL94?  I can't.  Edit, nope, M20E is not listed on the Swift site.  So great, the world does to UL94 and your airplane is now worthless and not flyable.

Most 200 HP IO-360s can't.  My 180 hp AEIO-360 on my other airplane was originally certified for 91/96, so can.

 

While I don’t have data on UL-94, we all should be able to with ADI.

We could run Mogas too engine wise, but I suspect there would be some kind of airframe mod because of the different vapor pressure causing vapor lock.

Having said that it’s likely that Mogas may not be today’s Auto fuel, I say that as auto fuel changes significantly by area, Urban Auto fuel is blended to pollute less, and Summer Auto fuel differs significantly from Winter, and of course California has their own Auto fuel, the huge price difference isn’t apparently all taxes.

‘Apparently even E85, isn’t. Seems it can be anything from 51% to 83% ETH https://en.wikipedia.org/wiki/E85 

As there are so many different fuels plus the fact it may change again in the future it might be difficult to Certify to. Company I worked for wasted a lot of time and money trying to Certify a Turbine to burn Bio-Diesel but couldn’t because Bio-Diesel isn’t really defined, it can be and is many different things both plant and animal fat based for example.

But I assume 94UL is made to an ASTM standard? If it really is just 100 LL without the lead it should have the same vapor pressure and there shouldn’t be any compatibility issue. Again I have never even seen 94 UL, so what little I think I know could be wrong.

As it sits now from what little data I have I don’t see anything with less risk and could be implemented with less cost and faster than 94UL, and ADI if you need it, a great many won’t. Most of GA carbureted fleet won’t. I think it safe to say that any aircraft that are eligible to burn Mogas could burn 94UL.

Might be worth reading https://www.lycoming.com/content/unleaded-fuels-part-1

 

Edited February 8 by A64Pilot

[T. Peterson]

On 2/3/2025 at 12:13 PM, 76Srat said:

. . . well, not quite.  Here's my thought:  Just like you guys, I've been reading just about everything I can find on the boiling EAGLE/100LL/unleaded debate/debacle/call-it-what-you-will issue.  And I apologize if this specific idea has been thrown around in here and I just can't find it, but I've been wondering a lot if we're simply missing the point altogether here.  Instead of wringing our hands over unleaded fuel options du jour and all of the worries with supply chain, distribution, pricing, loyalties between suppliers, does-it-play-well-with-others, etc?, should we get to pondering a larger opportunity?  

With credit to the latest article on the topic in this month's "EAA Sport Aviation" magazine, I think the solution might be in not trying to proffer the best "fuel" alternative and instead proffer the best reciprocating engine alternatives.  What do I mean by this?  Well, for starters, we have to wonder if on the fuel/engine side we're sitting on an upcoming sea-change in technology, not on the fuel side, but on the engine side.  And in support of this (possibly) exciting change, should we look no further than what has happened with avionics since the day the GNS430 was born?

Cue the logical coffee spewing over computer screens at this point, and I'm not trying to stir a long-tormented hornet's nest, but since the certification process is what it is (anything but cheap), should we as the marketplace look for a cheaper/viable engine replacement program instead of just pushing the rope further uphill on fuel alternatives?  The real answer lies in the cert process and the example shown us from those who dared to tread the shark-filled void of avionics upgrades, circa late 1990s.  It was said then, as it is being said now for engines in legacy types such as our beloved Mooneys, that "uprooting the legacy steam-gauges will never catch on" in the legacy piston fleet.  We see now how short-sighted that viewpoint was then and just how great it has been since.

I agree that there are legion reasons a recip engine replacement wouldn't be viable or feasible for most, if not all legacy piston fleets.  But, long term, a viable SAF-burning alternative recip engine for IO-320/360/IO-470/520/550 fleets out there seems to me to be money far better spent toward certification than a yet-to-be-determined acceptance rate of unleaded fuel replacements.  It is less than ironic to me that in the time you have to wait for a FOH we'll likely have the debate over the very unleaded fuel we'll be forced to use in that FOH solved--this is not a sustainable logic.  Let's put that effort in to gaining the best engine replacement for a longer term, instead of wasting this decade-plus over a fuel to be burned in engines that aren't sustainable themselves.   

We now have streaming and digital music.  Is this entire debate about unleaded avgas replacement going to end up being the VHS/Betamax debate?  Fast forward 5 or 10 years from now and will this fuel debate end up on the academic editing room floor, when we really should be debating not if, but which recip alternatives should be out there? 

Just read through the whole thread. Lots of gainsayers, but I like how you think. I don’t discount some of the other solutions, but I would love to see an answer from the engine side also!

[1980Mooney]

1 hour ago, T. Peterson said:

Just read through the whole thread. Lots of gainsayers, but I like how you think. I don’t discount some of the other solutions, but I would love to see an answer from the engine side also!

Our current engines and fuels are optimized for power, weight, functionality, simplicity and reliability.  "viable SAF-burning alternative" sounds fine but there will be unintended consequences.  E85 weighs 10% more than a gal. of Avgas and a gallon of E85 only has 79% of the energy (BTU's) of Avgas.  Less energy density - who cares?  Well maybe not if you are flying a 182 or a Dakota.  But if you are in a Mooney, with limited Useful Load as it is, it can really limit the usefulness of our planes. A pound of Avgas has about 18.75K BTU.  A pound of E85 only has 13.5 K BTU (some less).  That means you need to haul an extra 39% more pounds of fuel to make the same trip.  

For those with the efficient 4 cylinders that might mean a 4 hour trip with half hour reserve, the fuel required will weigh an extra 105 lbs. (57 gal E85 vs 45 gal Avgas)

But for those with the big 6's - many times we make a 4.5 hour trip with half hour reserve - I plan on 15 gph.  That is 75 gallons Avgas.  But with E85 the fuel required will weigh and extra 176 lbs.  (104 gal E85 vs 75 gal Avgas).  We will not be making that trip - extra fuel stops.

If you are thinking about automotive efficiency and power then you need a solid block, water cooling and a lot, lot more complexity.  And diesel? Look at the current Cont and Austro diesel solutions - tremendous complexity and not light.  And DeltaHawk?....they are less complex but they are in their umpteenth redesign trying to shed weight to become competitive - it remains to be seen if their 2 stroke will be efficient.  

[McMooney]

1 hour ago, 1980Mooney said:

Our current engines and fuels are optimized for power, weight, functionality, simplicity and reliability.  "viable SAF-burning alternative" sounds fine but there will be unintended consequences.  E85 weighs 10% more than a gal. of Avgas and a gallon of E85 only has 79% of the energy (BTU's) of Avgas.  Less energy density - who cares?  Well maybe not if you are flying a 182 or a Dakota.  But if you are in a Mooney, with limited Useful Load as it is, it can really limit the usefulness of our planes. A pound of Avgas has about 18.75K BTU.  A pound of E85 only has 13.5 K BTU (some less).  That means you need to haul an extra 39% more pounds of fuel to make the same trip.  

For those with the efficient 4 cylinders that might mean a 4 hour trip with half hour reserve, the fuel required will weigh an extra 105 lbs. (57 gal E85 vs 45 gal Avgas)

But for those with the big 6's - many times we make a 4.5 hour trip with half hour reserve - I plan on 15 gph.  That is 75 gallons Avgas.  But with E85 the fuel required will weigh and extra 176 lbs.  (104 gal E85 vs 75 gal Avgas).  We will not be making that trip - extra fuel stops.

If you are thinking about automotive efficiency and power then you need a solid block, water cooling and a lot, lot more complexity.  And diesel? Look at the current Cont and Austro diesel solutions - tremendous complexity and not light.  And DeltaHawk?....they are less complex but they are in their umpteenth redesign trying to shed weight to become competitive - it remains to be seen if their 2 stroke will be efficient.  

I don't know about the continental diesel but the austro isn't overly complex.  yes you have a turbo but you also have no ignition system, no plugs, wires, distributor etc...

there will be tradeoffs no matter what we do but i'd accept a higher hp engine burning  75% of the fuel for a 150ish lb diff.  also given more hp, thinking they could increase ul a bit to offset some.

 

Edited February 9 by McMooney

[Ibra]

On 2/5/2025 at 1:46 AM, A64Pilot said:

Dodge has an engine that makes over 1,000 HP on E-85, and it even passes emissions

Even 1600hp on Jeskos with E85 on Octane < MON91

https://www.roadandtrack.com/new-cars/car-technology/a27029039/koenigsegg-jesko-engine-explained/

Clever and innovative stuff (these words unheard of in aviation context) 

Then you have the problem of alcohol in fuel system, airframe…but again sports cars don’t have much of these issues (ahem, regulatory limitation or lack of imagination). On limitations, I think all non-turbos Mooneys should be able to run UL94 (assuming they can have variable timing) as long as one sacrifies some power and plan for extra more runway length on takeoff. 

We flew uncertified with IO360 using UL91 (MON91) and SP98(MON88), these have less octane than UL94 and 100LL, the temperatures were slightly hot on takeoff but other than that “it works”, yet they are not approved by Lycoming !

Edited February 9 by Ibra

[EricJ]

1 hour ago, Ibra said:

Even 1600hp on Jeskos with E85 on Octane < MON91

https://www.roadandtrack.com/new-cars/car-technology/a27029039/koenigsegg-jesko-engine-explained/

Clever and innovative stuff (these words unheard of in aviation context) 

Continuing my interest in how the Germans managed this in WWII, the Daimler DB 605 V12 engines that powered things like the Me109 made around 1800 hp with a design spec fuel of 87 Octane.    On that fuel they could run 43.4 inhg MAP, and with the later 90/100 fuel they could make nearly 60 inhg MAP.   If the 90/100 fuel wasn't available and they had to run the old spec fuel (which happened a lot), they were restricted to 43.4 in MAP.

I don't know how they did that, but clearly it's possible.

 

[A64Pilot]

45 minutes ago, EricJ said:

Continuing my interest in how the Germans managed this in WWII, the Daimler DB 605 V12 engines that powered things like the Me109 made around 1800 hp with a design spec fuel of 87 Octane.    On that fuel they could run 43.4 inhg MAP, and with the later 90/100 fuel they could make nearly 60 inhg MAP.   If the 90/100 fuel wasn't available and they had to run the old spec fuel (which happened a lot), they were restricted to 43.4 in MAP.

I don't know how they did that, but clearly it's possible.

 

In MP isn’t much boost for starters. For instance the 30 PSI in my Motorhome is when added to the 14.7 PSI atmospheric is around 90 inhg in MP.

You get roughly 30 in per 15 PSI of course.

But secondly assuming it’s like the old Pratt’s like the R-1340 with its Supercharger that had a T/O rating from memory of around 40 something inches it had roughly again from memory a compression ratio of about 6 to 1. That’s why you can prop a 1340 cuin engine. It will run just fine on standard 87 car pump gas and I’m sure lower.

Now the 1340 evolved over the years of course as it first flew I think in 1925? So HP and boost I’m sure varied greatly and I’ve not seen a 1340 with ADI which would allow much more boost. The twin row Wasp R-1830 did of course run ADI.

The older DB-601 Benz motors in the BF-109 apparently couldn’t make much boost, they didn’t get a HP boost from 100 Octane like the Merlin did. I think the later DB-605 engine could though

Germans ran ADI for high boost and Nitrous Oxide for very high altitude

I’m pretty sure they carried enough ETH/water for at least 20 min of use.

All this is from memory, and my memory may be a little wrong, but I believe ADI was exceedingly common in WWII and it of course significantly increased HP.

The US 4360 on T/O burned 3,000 lb per hour without ADI, but 2500 an hour with ADI and made significantly more power in a “wet” takeoff.

Again from memory.

 

Edited February 9 by A64Pilot

[jlunseth]

Hey folks. The word "troll" comes to mind. Ten whole posts and almost all are on the idea that all of GA should replace all of its engines. Really not worth responding to.

[1980Mooney]

21 hours ago, McMooney said:

I don't know about the continental diesel but the austro isn't overly complex.  yes you have a turbo but you also have no ignition system, no plugs, wires, distributor etc...

there will be tradeoffs no matter what we do but i'd accept a higher hp engine burning  75% of the fuel for a 150ish lb diff.  also given more hp, thinking they could increase ul a bit to offset some.

"austro isn't overly complex" - well it is like art or beauty I guess and in the eye of the beholder.  The Austro has dual overhead cams, 4 valves per cylinder, chain cam belt, high pressure direct fuel injection, a gearbox to reduce rpm.  "no plugs, wires" - well not exactly right because you have to have "glow plugs and wires".  Because of durability problems with the original Thielert, Austro went with a cast iron block that added about 120 lbs. alone.

[Pinecone]

On 2/8/2025 at 4:35 PM, A64Pilot said:

 

As it sits now from what little data I have I don’t see anything with less risk and could be implemented with less cost and faster than 94UL, and ADI if you need it, a great many won’t. Most of GA carbureted fleet won’t. I think it safe to say that any aircraft that are eligible to burn Mogas could burn 94UL.

And what percentage of the Mooney fleet is carbureted?  

[76Srat]

5 hours ago, jlunseth said:

Hey folks. The word "troll" comes to mind. Ten whole posts and almost all are on the idea that all of GA should replace all of its engines. Really not worth responding to.

Thanks for your take on this, @jlunseth.  I appreciate the concern.  That said, I am thrilled that there has been the response to this topic.  While I'd love to see "that all of GA should replace all of its engines", that certainly will never happen, much less happen in my lifetime.

Overall, my attempt at getting us to think about a lot more than just the energy and time (and $$$) in getting 100UL replacement fuel(s) certified is time well-spent.  I appreciate your take, for sure, but would never consider all of the input here not worth responding to--it's valuable insight into our collective mindset.  I argue that such collective mindset should be expanded beyond just considering the benefits (and costs) associated with 100UL replacement.  It should go far beyond that if we really do value preserving the utility of our Mooneys for more than a few more years.   

[76Srat]

On 2/9/2025 at 8:05 AM, T. Peterson said:

Just read through the whole thread. Lots of gainsayers, but I like how you think. I don’t discount some of the other solutions, but I would love to see an answer from the engine side also!

Thanks for supporting the topic, @T. Peterson.  I agree with everything said on here, some more than others, of course.  My hope is that we start/continue to think far beyond just the fuel issues and look to support the progress, investment and anyone who supports a more efficient/simplified certification process to give our Mooneys and their owners more options when it comes to powering them for the next generation.  I submit that merely looking at the fuel equation and fuel options will certainly help in the short-term, but isn't a viable long-term solution.  Only a fresh, new, innovative power plant upgrade(s) will do the trick.  It's either that, or extinction of the mark will be inevitable.  I'd hate to see that happen.  

With DOGE and the over-due look at government inefficiencies that's taking place currently, it'll only be a matter of time before we'll see our very world become a blip on the map of history (see the upcoming sea-changes to privatizing air traffic control, flight planning, etc., that is just around the corner, for example.  DOGE has already held up the Euro/Canadian model as "the best" from an economic standpoint, which I can't disagree with from a pure efficiency/operating cost-benefit analysis, but I'm scrambling to find reasons to agree operationally from a user's viewpoint, primarily because there aren't near the number of operations in Canada and the whole of Europe combined in a week as we have every single day in the US).  Let's not let our lack of considering other power options/engineering mean the end of the line for legacy single engine piston aviation.  Fuel alternatives alone will not save it.

Everyone who has expressed a concern about the outright costs of re-engining the fleet or pursuing and obtaining a completely new recip engine program for Mooneys and other legacy single engine piston aircraft is correct--it just will never make economic sense to do so.  I can't argue with that.  What I am suggesting is that we learn from our Cirrus brothers and sisters who, by way of not selling or marketing a "new, safer alternative aircraft", but instead have done a hall-of-fame job marketing a lifestyle brand differently than all other aviation manufacturers had ever done before, we can save the entire single engine piston fleet.  

What have Textron/Beech/Cessna/Piper ever done to make anyone not already involved in general aviation think that they should become involved?  A lot, if you're talking about post-WWII pilots earning their civilian wings after the war and into the boomer years under the GI Bill.  But literally zero after that, at least by way of marketing and innovative ways to bring in more people to GA.  Zilch.  Enter Cirrus.  I loath Cirrus and love Cirrus, all at the same time.  I loathe them for producing an inherently unstable airframe that I believe is far inferior to Mooney.  I LOVE them for single handedly rescuing single engine piston aviation.  Without Cirrus, we'd be stuck in the rut that Cessna/Textron have hewn through the decades of stale thinking, stale engineering and without Congressional support in tax deduction/depreciation legislation, would have run all of piston aviation into the museum by now.

Sorry for the rabbit-hole of topics here on this reply to your post (to my OP), but that's my intent with this thread--get us all thinking outside the box of merely supporting a 100UL replacement, which is what we should all be doing anyway, and on to more grandiose goals of securing the operational future of all of piston aviation for the next generations and beyond.  It will not survive if we're focused merely on fuels . . . 

[A64Pilot]

22 hours ago, Pinecone said:

And what percentage of the Mooney fleet is carbureted?  

I have no idea, the rest of us like me in my J can run ADI that has a number attached to it of $12K and I think 40 ish lbs

None of the options are going to come without drawbacks, but $ 12K and 40 lbs I could stomach, I’d rather keep 100 LL myself though.

I think if tied to a lightweight battery the 40 lbs could be reduced some and keep the CG within range if the ADI system were mounted behind the aft baggage compt wall, bigger Mooney’s may be able to simply remove some of the Charlie weights.

For $12K I’d like at least variable injection myself, but everything in Aviation costs more than it should. I mean $100K for a big VW engine for example, it’s just the way it is and it’s not going to get better.

IF we accept that lead has to go, personally I don’t accept that but I don’t count for squat. It seems we have maybe three possible solutions.

1. A new “Magic” fuel, that so far no one has been able to formulate. Now personally I think it’s possible, but maybe not feasible cost wise. Seems so far every possible candidate “eats” paint and bladders and other fuel system components and my bet is that it’s effect on health is probably worse than 100LL, but again I’m no expert, but if you do some reading many are raising the flag on aeromatics in Auto fuel based on its effect on health. Are they just nuts? Possibly I don’t know

2. A new engine, some think it could be done for less than $100K and or $100K isn’t much, but for me I think I’d go Experimental or something else first. $100K would push me out of flying. I don’t think it can be done for even close to $100K myself. I think it would be much higher. The scale wouldn’t be there as we would be talking a few a month, not hundreds or thousands that it would take for economy of scale to kick in.

I think the requirement of a new engine would kill GA as I think adding more than $100K to every airplane out there would first make the majority of the GA fleet essentially worthless, probably boost the Hell out of LSA’s and Rotax would love it though.

3. ADI for those that need it, apparently 20% of the GA fleet and 94UL alone for the 80% of the fleet that doesn’t. They claim Turbo aircraft can also work with ADI, but does that mean continuous injection? I don’t know, maybe? That’s where I think variable injection would help.

Of those three things, only ADI exists, the other two are at this time Vaporware. Perhaps that’s what we need to keep being able to get 100 LL, Vaporware.

For decades the Major Auto manufacturers convinced the powers that be and by that I mean CARB that EV’s weren’t a viable platform, that Hydrogen is what we need and it’s only a couple of years away. Hydrogen powered Auto’s are and always have been Vaporware, but touting it kept the Auto manufacturers continuing to build ICE cars which is what they wanted of course.

I have nothing against ICE cars, I own a few, just saying the strategy worked is all.

 

Edited Tuesday at 04:43 PM by A64Pilot

[N201MKTurbo]

I read a book once that was published in the late 1920s about gasoline. Nothing they are talking about today wasn’t in that book. So, thinking that some magic fuel will be discovered is crazy.

Would our engines run on E85? Sure they would, but E85 has about 80% of the energy of 100LL, so you would lose a lot of range. And E85 has its own material compatibility issues.

100LL = 112530 BTU/gal

E85 = 88258 BTU/gal

If it takes 16 GPH to make 200HP with 100LL, it will take 20.4 GPH to make 200HP with E85.

[A64Pilot]

1

3 hours ago, N201MKTurbo said:

If it takes 16 GPH to make 200HP with 100LL, it will take 20.4 GPH to make 200HP with E85.

It’s not quite that simple because the higher Octane allows advanced timing, but I agree that fuel consumption would increase significantly.

But E85 is way more than 20% cheaper than 100LL, so range loss yes, but at the cost to fill up I’d take it.

But I don’t think the compatibility would be the big issue with E 85, it’s it’s affinity for water, water that likely would come out of suspension at higher altitude and lower temps that I think would make it less than ideal as an aviation fuel.

The thing is that it seems like some kind of drop in replacement for 100 LL just ain’t happening, everything will have something that makes it less desirable than 100 LL, starting in my opinion with the price. I just don’t believe anything that comes out, if anything does is going to be only a buck a gl more. Maybe an Alaska gl price buck, but not a Fl US gallon price. I just think Monopolies are sort of known for bending you over the table price wise. Look at Pharmaceuticals for instance once they lose the monopoly see what happens to the generic price. 

 

[MikeOH]

@A64Pilot

So, I thought the idea was to ADD alcohol to fuel to absorb water when operating at high/cold altitudes???  Why are you then concerned with E85's affinity for water?  Seems contradictory.

[N201MKTurbo]

I just read an article where they took a blown racing engine and tuned it for max HP with leaded race gas and then tuned it for E85. I am assuming the race gas is similar to 100LL. They got a few percent more HP with E85. They attributed it to the cooling effect of vaporizing the E85. It was a carb engine.

It seems that E85 won’t work as a drop in replacement in our engines. Our engines would need the fuel flows increased. This is an easy mod, but you won’t be able to switch back and forth between E85 and 100LL.

Flex fuel cars have electronic fuel injection systems that adjust the mixture according to what you put in your tank.

[hammdo]

Like my Camaro on e85 - I need 30% more fuel to run - on cold days I have it set for even more to kick it off. I would find it hard to use without some form of computer/ecm. Cooler running and more power - its even hooked on ‘meth’anol ;o)

-Don

[EricJ]

2 hours ago, N201MKTurbo said:

I just read an article where they took a blown racing engine and tuned it for max HP with leaded race gas and then tuned it for E85. I am assuming the race gas is similar to 100LL. They got a few percent more HP with E85. They attributed it to the cooling effect of vaporizing the E85. It was a carb engine.

It seems that E85 won’t work as a drop in replacement in our engines. Our engines would need the fuel flows increased. This is an easy mod, but you won’t be able to switch back and forth between E85 and 100LL.

Flex fuel cars have electronic fuel injection systems that adjust the mixture according to what you put in your tank.

A common racing mod is using E85, since the engine can be tuned to make more power with it, but it does require changes, like bigger injectors.  The base octane rating of E85 is 105, so way better than premium pump gas.  Another significant downside of E85 is that it spoils.    Just sitting by itself it goes bad, and needs to be used while fresh.   That's problematic for most applications.

 

[Pinecone]

MOGAS is not the answer.  It is too variable.  And in some areas, impossible to find without ethanol.

E85 would have more issues with seals, o-rings and hoses than G100UL.  And alcohols are NOT nice with aluminum.

Ask the boating world about issues with MOGAS with alcohol and the problems they had.

So, if we decide on MOGAS and ADI systems, what happens to those low number planes that no one STCs a system for?  And what about vapor pressure issues that some aircraft require a boost pump mounted near the tanks to push the fuel.  Where does that go in our Mooneys?  And who does the STC for that?