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Mogas vs. 100LL?

One minor word of caution: Cessna 172's are not very prone to vapor lock because the high wing fuel tank provides good head pressure to the fuel pump or carburetor. Low wing aircraft and steep climb angles, on the other hand, can more readily develop vapor lock issues . Some folks running auto fuel in their RV's have installed electric fuel pumps at or near each wing root to help ensure positive pressure and low vapor enter the pumps under conditions conducive to vapor lock.

Skylor

I agree. Our low wing configuration is all gravity feed to the center tank. The dual pumps are located at or near the lowest part in the fuel line plumbing, right at the center tank. There should always be positive pressure to the pump (s).
 
Question for you engine tuners...as we plan to burn both 93U E10 and 100LL, with the ECU being programmed only for 93U, what will the default program do when burning 100LL? Will it burn richer than the Mogas?
 
Just a data point

Just a data point here. I was in Davis, CA two days ago.
At the airport (EDU) the price of 100LL was $4.07 ($4.02 if pre-paid), and the price for 87 at the pump was $3.87.

I was suprised at only a 20 cent spread between the two.

Avgas.jpg
 
Just a data point here. I was in Davis, CA two days ago.
At the airport (EDU) the price of 100LL was $4.07 ($4.02 if pre-paid), and the price for 87 at the pump was $3.87.

I was suprised at only a 20 cent spread between the two.

Avgas.jpg

Wow...100LL is $4.50/gallon here in North Texas.
 
Interesting data on what happens to "old" fuel from the Project Farm guy.

https://www.youtube.com/watch?v=UvS_D4_lF5U

I have no plans to run fuel with ethanol, but i included all the right kinds of rubber in my system that "should" handle ethanol. I was not expecting what he saw with respect to aluminum corrosion. Can't imagine this is good for our fuel tanks.
 
Valve stem lubrication ?

I recently experienced a stuck exhaust valve on mogas. Above in this thread it was proposed that some lead does help lubrication. Yet, others share how they run TBO on mogas with no issues. Any comments to share ?
 
Interesting data on what happens to "old" fuel from the Project Farm guy.

https://www.youtube.com/watch?v=UvS_D4_lF5U

I have no plans to run fuel with ethanol, but i included all the right kinds of rubber in my system that "should" handle ethanol. I was not expecting what he saw with respect to aluminum corrosion. Can't imagine this is good for our fuel tanks.

So I have to ask, what was the composition of the metal in these test? It looked more like "white metal" casting material. It certainly wasn't 2024 alum like what our RV tanks are made of.
It's interesting that I have been running 93 OCT E10 auto gas for the last 10 years of more, and don't see any corrosion when I inspect the tanks.
 
If you have high compression and or close cowl hot running aircraft engine Mogas is not ideal or even practical or safe.

The price you quote is NOT for Motor Gas (Mogas FAA approved fuel by STC in certified planes and found at airports). Currently Mogas is almost $4 and 100LL $5 a gallon. Not much cheaper. If you want automotive gas at the corner station that is another issue.

  • Lower vapor pressure of 100LL can (and does) resist and prevent vapor lock and loss of power.
  • Automotive fuel (from the corner station) can have ethanol and do nasty things to aircraft seals.
  • Lower octane of Mogas and Automotive gas means high chance of detonation and engine damage.
  • If you buy gas from corner gas station you must haul & transfer it to plane, which opens up a host of issues (contamination, spills, fire).
  • Mogas is only$1/gal cheaper and not widely available.
Up to you.

ALL THESE ISSUES CAN BE ADDRESSED AND MITIGATED BUT NOT ELIMINATED. Pulling up to the pumps or having fuel truck at the airport fill your plane with100LL is best IMHO.

Mogas at $1 cheaper than 100LL is not easy to find. Again high compression and tight cowl (hot running fuel system) is not really suited for Mogas or Automotive gas.
 
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Just like everything else in life there are different ideas about how to do things and there are consequences.

For me, AV gas is $2 a gallon more at the airport, but $1 a gallon more at an off airport fuel vendor. This is compared to a fleet fueling station nearby that has 91 non-eth.

So, I bought a 72 gallon tank for the bed of my truck and typically run 75/25. The result is very decent fuel at around $1.50 cheaper per gallon. At 7gph and 125 hours a year, that saves me around $1300 a year while not pouring complete garbage in the tank.

This is a reasonable trade off for me. If I was forced to run ethanol, I wouldn’t touch the stuff.
 
Each to their own of course cause that's what Experimental is all about BUT unlike a vehicle you just cant pull over when the engine fails or starts acting up. I value my life a lot more than saving a few bucks here and there for cheap fuel in my Lyc!
 
I do admire the true Experimental guys. Their innovation has truly helped move General Aviation forward. But I’m not that guy. I don’t know enough to experiment with something that might force a return to Earth at a time and place not of my choosing. For me personally...Experimental aviation stops forward of the firewall. I’ll switch to mogas just as soon as an alternative that is approved by Lycoming for my engine is available on the fuel truck at my airport.
 
To both Capt and MacCool, there is the opportunity to enlighten yourself, and there's plenty of information freely available from credible sources to do so.

20min 30sec onwards is worth listening to in the following presentation from Mike Busch at Savvy Aviation (in fact all Mike's presentations are worth listening to):
https://www.youtube.com/watch?v=AEGyN2U3FSM
If you can't be bothered listening to it, then I'll spell out his comments:
"... lead is a good octane improver, but it's absolutely disastrously in all other respects."

Trying to play out mogas users as just being tightwads is just straight up incorrect. Lead does not belong in naturally aspirated aircraft engines running at 8.5:1 compression ratio's and lower (some would argue higher with the right timing), and that is supported by Lycoming, who approve the use of unleaded mogas in almost every Lycoming engine 8.5 and lower:

https://www.lycoming.com/sites/default/files/SI1070AB Specified Fuels.pdf

From stuck valves caused by lead condensate (more common in Lycoming's because of their cooler sodium filled valves) to the tetraethyl lead combining with ethelyne dibromide to form the salt lead bromide (see the link below from Shell) lead in fuel is just brutal to internal combustion engines:

https://www.shell.com/business-cust...entre/technical-talk/techart-18-30071600.html

As we all know, water vapor is one of the byproduct of hydrocarbon combustion, which ends up in your crankcase as blowby gasses. Mix water and salt and leave it on an iron camshaft and of course you're going to end up with corrosion. I just got a notice today of an O-320 that had a prop strike here and was pulled apart to find the engine was in great conditions, except the crank was covered in corrosion (the owner was a diehard avgas user and is now up for a further $7k). There's a reason we don't hear of car engines having corrosion issues anymore. The sale of lead in auto fuel was banned in this country 19 years ago.

And if you don't think fueling mishaps occur with aviation fuels, you are seriously mistaken.

When I pump fuel into my aircraft it all goes through a filter that I have verified the micron rating and other critical specifications. I put it through a clear fuel bowl so that I can determine the batch color as a visual indicator. I can verify the vapor pressure, ethanol content and so-on. You don't know any of this when the fuel truck pulls up and pumps it into your aircraft, as Bob Hoover found out the hard way.
https://blog.aopa.org/aopa/2016/01/11/misfueled/

Those Australians in the crowd will never forget the biggest fuel contamination issue in the nations history of course happened with, yes you guessed it, avgas. Not only did it ground half the entire aircraft fleet in Australia, it resulted in some very expensive equipment replacements:

http://avstop.com/news/avgas.html#:... in the dosage,the contamination of this fuel.

Using avgas in aircraft that do not require it simply gives the aviation community a bad name and makes the public want to shut us down even harder. All we really do when we use it is threaten its availability for those warbirds and high compression aircraft that really do need it. Based on the list published by Lycoming I would approximate that 80% of engines don't need to be running leaded fuel. We should be leaving it for those who really do so that the classics of aviation can continue to fly.

Rant over.

Tom
RV-7
IO-360M1B that only drinks Mogas.
 
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I do admire the true Experimental guys. Their innovation has truly helped move General Aviation forward. But I’m not that guy. I don’t know enough to experiment with something that might force a return to Earth at a time and place not of my choosing. For me personally...Experimental aviation stops forward of the firewall. I’ll switch to mogas just as soon as an alternative that is approved by Lycoming for my engine is available on the fuel truck at my airport.

Here's all the places in Minnesota where you can buy non-ethanol unleaded gas. https://www.pure-gas.org/extensions/maps.jsp?statecode=MN

Just think, throw a couple of 5 gallon jugs in the truck and stop on the way to the airport. Mix that in with the 100LL you buy at the airport. And, you could save $10 to $15 (over what you're paying now) every time you fly. And, your plugs and valve guides would thank you.
 
Thanks Tom. I read Mike Busch’s stuff, have watched the YouTube video you referenced, follow Savvy Aviation, and read a lot about aircraft fuel. I’m fully aware of the evils of lead in gasoline, its effects on engines, the environment, and humans, and will enthusiastically switch to an unleaded version in my airplane just as soon as the stuff on the fuel truck at my airport is OK with Lycoming and my A&P gives it a thumbs up. I guess I’m saying I don’t need the education (but thank you very much)....I just need the fuel to be approved and available.

And by available, I mean on the fuel truck or at the airport. My car has less luggage capacity than my RV...there isn’t room for even one 5 gallon jug.
 
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I have a fuel injected engine (strike 1), Pmag (strike 2), best around me is 91 with no source of 93 in hundreds of miles (strike 3).

I want to run the stuff but I just don't feel like playing with fire. As far as saving are concerned, the Pmag already does that for me. haha 7-7.6 GPH LOP already saves me a boat load.
 
Why Pay So Much For a Transfer Tank?

For doing fuel transfers, 55-gallon steel drum and a barrel pump are in my future.

Buying 100LL from a local fuel supplier will save a $1 per gallon, than what the fuel pump price is at the airport.

You can buy 55-gal drums from most wholesale / retail fuel suppliers. This would be a brand new drum, not a used one.

You can even get the proper labels from them for transportation.

Best regards,
Mike Bauer
 
Here's all the places in Minnesota where you can buy non-ethanol unleaded gas. https://www.pure-gas.org/extensions/maps.jsp?statecode=MN

Actually, there are far more places that aren't listed on that map, at least around here. Here in the middle of the state it's lake country and no one wants to put ethanol fuel in their boat. Many gas stations up here have non-ethanol 91 octane at the pump.

I always keep plenty of gas on the premises. This 150 gallon tank recently replaced the one that I'd had for 30 years. The local oil company (listed on the map you linked BTW) delivers non-ethanol 91 AKI with just a phone call and I can just tow it down to my dock when the boats need gas. Very convenient.

But it's only 91 octane, so not "Lycoming Approved" for my airplane engine according to SI1070AB.

...
 

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Obsession with Ethanol?

I just can't understand this ongoing obsession with Ethanol.
It is simply not a problem in a Lycoming engine with 8.5 to 1 or less compression ratios.
I have a fuel injected engine (strike 1), Pmag (strike 2), best around me is 91
A fuel injected engine is a plus and 91 Octane E10 is perfectly good to use.
Don't know anything about P-mags and why those would be a strike??
summed it up nicely, lead is pure evil in a Lycoming
and most of us know by now that 100octane is needed to run some small percentage of the GA fleet but we certainly have the ability to set up our engines for 91E10 which is available everywhere.
Automotive fuel (from the corner station) can have ethanol and do nasty things to aircraft seals
No it doesn't, not in my airplane after10 years of using 91E10,
that's mogas with ethanol.
We know that seals dry up and get brittle after years of exposure to 100LL but we simply accept that as a known devil. Ethanol does have a softening effect on some seals over time but "nasty things" is what 100LL does to rubber seals.

As far as transporting fuel, every county and airport has their own rules and what works here might not work there.
There are plenty of us RVers who have burned mogas for decades, some with thousands of hour without issues. To each his own.
 
A fuel injected engine is a plus and 91 Octane E10 is perfectly good to use.
Don't know anything about P-mags and why those would be a strike??

Fuel injected is a strike in my mind because of their ability to "run" on the ground while heat soaked on a hot day. Auto fuel will make it worse.

Lower octane reduces detonation margin.

P-mags advance timing (many will argue too aggressively) which reduces detonation margin.

Can it be done? I'm sure it can, and I'm sure people do. It's a risk I'm not really willing to take. Especially when I hear of one of my friends get into vapor lock on takeoff in his O-360 with standard mags. (don't know what octane he had but it was auto)
 
Avgas vs. Mogas EN228

Hello,
i fly since aproxx.. 3 Years, one Tank 100LL, and the other Tank Mogas (EN228) i have, and see no bad reactions also on warmer Days....
I Change every year Mogas and Avgas between the Tanks....(no Mix!)
Start and Landing always with Avgas, Cruising and further Cruise climb with Mogas....
Engine, Sparks and Oil Analyze shows no issues... (but i hab only 170 H Hobbs)
Maybe the leaning is a bit different.. during Leaning Process, EGT's comes a little bit earlyer with Mogas, and the CHT's are a few Degrees higher after Level Off with same Controll Levers Positions in higher ALtitude between the both Fuels....
what are your perceptions on this subject?

Greetings
Manfred
 
Hello,
i fly since aproxx.. 3 Years, one Tank 100LL, and the other Tank Mogas (EN228) i have, and see no bad reactions also on warmer Days....
I Change every year Mogas and Avgas between the Tanks....(no Mix!)
Start and Landing always with Avgas, Cruising and further Cruise climb with Mogas....
Engine, Sparks and Oil Analyze shows no issues... (but i hab only 170 H Hobbs)
Maybe the leaning is a bit different.. during Leaning Process, EGT's comes a little bit earlyer with Mogas, and the CHT's are a few Degrees higher after Level Off with same Controll Levers Positions in higher ALtitude between the both Fuels....
what are your perceptions on this subject?

Greetings
Manfred
Hi Manfred, this is a common technique for running mogas, and allows the best of both - safety and cost savings. I personally use only UL91 at this time, but might try mogas sometime in the future. I ran one tank of 100LL just for testing to see if there was any difference between 100LL and UL91, but they seemed almost identical in my application (RV-8, IO-360, AFP FM-200, PMAGS, red/silver paint :D)
 
Fuel injected is a strike in my mind because of their ability to "run" on the ground while heat soaked on a hot day. Auto fuel will make it worse.

If you install the SDS or EFII systems that has the fuel constantly circulating back to the tank, the vapor lock issues are non-existent. I meant zero. My engine starts even better when it is warmed.

I also run 93 mogas with 10% ethanol in my aircraft. No issues what so ever. I used to run Avgas on one side and mogas on the other. Made several tests and I cannot tell the difference between the two. It is probable that the mogas will make less power at 10K+ altitude. Have not been there yet.

I did run teflon lined hoses for all of my flex lines and all elastomers are viton to be compatible with the ethanol.
 
If you install the SDS or EFII systems that has the fuel constantly circulating back to the tank, the vapor lock issues are non-existent. I meant zero. My engine starts even better when it is warmed.

I also run 93 mogas with 10% ethanol in my aircraft. No issues what so ever. I used to run Avgas on one side and mogas on the other. Made several tests and I cannot tell the difference between the two. It is probable that the mogas will make less power at 10K+ altitude. Have not been there yet.

I did run teflon lined hoses for all of my flex lines and all elastomers are viton to be compatible with the ethanol.

Yes, with those systems/setup I could see how this problem would disappear.
 
Yes, with those systems/setup I could see how this problem would disappear.

Related to start-up = big yes.

Related to other operation = big unknown. A lot would depend on overall fuel system configuration/variables. Unless I'm not understanding the intended statement/idea above.
 
Related to start-up = big yes.

Related to other operation = big unknown. A lot would depend on overall fuel system configuration/variables. Unless I'm not understanding the intended statement/idea above.

True. Either way my current setup has what I would consider too much risk involved for me personally to run auto. I'm sure others do it with similar setups but it's just not a risk I'm willing to take; especially until I understand everything involved first.
 
It can be done, it's not impossible and it's not even as difficult as you make it out to be.

Those who say something is impossible should not mess with those that are doing it.
Did I say impossible? Nope. You just made a strawman argument. Just a hassle and loss of margin of safety. The savings is not worth it to me. I have read dozens and dozens of accident reports over the years caused by using Auto gas. You save what? A few bucks. Some run one tank Av gas for takeoff and landing, and switch to auto gas tank for cruise. That shows me how confident they are. I have seen it all. No thank you. Cheers
 
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Some run one tank Av gas for takeoff and landing, and switch to auto gas tank for cruise. That shows me how confident they are.

Well, this is a bit misleading. Little to do with confidence. The only time Mogas is questionable with regards to octane requirements is during full power operations, e.g., takeoff/climb. At lower power settings octane requirements go way down.
 
Not just octane, but more-so vapour pressure. Mogas boils at a much lower temperature. Takeoff and a balked landing cause the highest fuel flow, highest fuel line suction, thus highest chance of vapour lock right when it's going to have the highest consequence.
 
I recently experienced a stuck exhaust valve on mogas. Above in this thread it was proposed that some lead does help lubrication. Yet, others share how they run TBO on mogas with no issues. Any comments to share ?

Mike Busch seems to think it's the lead causing the stuck valves. They analyzed the deposits around the stem and found they were caused by TEL which reforms from a gaseous state because of the cooler sodium-filled valves on Lycs.

https://resources.savvyaviation.com/wp-content/uploads/articles_aopa/AOPA_2020-07_why-valves-stick.pdf
 
Each to their own of course cause that's what Experimental is all about BUT unlike a vehicle you just cant pull over when the engine fails or starts acting up. I value my life a lot more than saving a few bucks here and there for cheap fuel in my Lyc!

This is a fairly narrow scope of risk mitigation. You could also say the best way to eliminate risk is not fly at all, but the alternative is driving, which is significantly more dangerous that flying.

Let's say you save $1500 a year running 91 ethanol-free pump gas. In 10 years you have $15000 you can spend on the newest panel item or engine technology that gives significant safety margins over the old tech.

In fact, you could give all the credit in the World to us experimental types for advancing GA in significant ways. If Garmin or Dynon didn't have us in their market, there's simply no way we have the panels we have today in GA.

I'll go as far as saying the experiments some are doing today with fuel and ignition systems that reliably run unleaded auto fuel, will lead to paths for the elimination of TEL in aviation fuel. All this may seem crazy to some, but you can say all great advancements have a little crazy.
 
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Used the search function to find this thread. It appears to have started 3-years ago.

Fuel is not available on my home field.

I had a neighbor that moved away that used 93 ethanol free car gas in his RV for several years without issue.

Have a friend with an RV-6A 320 fixed pitch that has been using 93 ethanol free car gas for more than a year as 100LL where he is based is typically $2 USD more than ethanol free 93 octane car gas.

Well I decided to give it a try. One neighbor that sold his RV warned me to only use it in one tank till I get experience with it. He had issues sometimes when he used it in his RV and would get vapor lock because of the 93 ethanol free car gas. They say great minds think alike as I was only planning on running the 93 ethanol free car gas in one tank till I had experience with it.

Experiment started with running the right tank low on 100LL then adding the 93 ethanol free car gas. I started the experiment with 10-gallons. My carb equipped 320 with CS prop did not notice any different on a cold engine starting or flying. I purchased another 20-gallons. After several refueling of the right tank with the mogas (will use mogas the rest of the post for the 93 octane ethanol free car gas and yes I purchased a tester to test for alcohol content) I landed and taxi in on the mogas. Next time (cold engine) I used it to start on, taxi out, runup, and takeoff without issue.

Neighbor took his new to him B36 to another airport for his first annual inspection. I transported him home on mogas after taking off on 100LL. When his airplane was done, I flew him back on mogas and during a LONG taxi, had vapor lock and the engine stalled. I had just been cleared to cross a runway and told ground that my engine just stalled and will call them back after restart. Switched tank and engine started back up. Told ground that I has now ready to cross the runway. OAT was in the 70s and it was not hot but engine oil temperature was 195. Have had vapor lock issues with 100LL on the ground in hot southern Kalifornia during initial flight testing with oil temperatures over 230. Appears that the margin is a lot less for mogas. Used 100LL for takeoff and switched to mogas for enroute cruise home and landed on mogas.

After sitting two weeks, I wanted to go on a local flight. This was starting on mogas after a longer than usual period of inactivity. This was one of the hardest engine starts that I have ever experienced. All eventually ran smooth and takeoff was uneventful.

The plan was to run the right tank as low as I dare and refill both tanks with 100LL. Today's flight ran the right tank down to between 2 and 3 gallons on the Dynon EMS gauge. Landed and filled both tanks up with 18.84 gallons of 100LL. Math says that 15.84 gallons went into the right tank that holds 19 gallons. Restart was uneventful on the right tank. The runway is 5,501' and that is pretty close to my taxi distance for take off. About 50' before reaching my runup area, engine stalls. Oil temp was 188 and OAT was just below 80F. I was taxing with the boost pump on just like Lycoming recommends with a hot engine. Did that all the time when I was based in SoCAL. Switched tanks to the left than has only had 100LL added to it since I built the airplane and no start. Get out of airplane to let starter cool off. After three times repeating this, I turned boost pump on and took a fuel sample out of the gascolator to check for water and debri. Fuel was 'straw' color like mogas. Call neighbor on my cell phone to see if he could fly my portable jump starter battery box to me if the next attempt to start did not work. Next attempt at starting had the engine running but missing. Engine smoother out running it at higher mag check RPM, completed runup, and takeoff uneventfully. 3 or 4 miles away from the airport, I made a radio call that I was 9-miles out, crossing over the airport and would land on 27. My neighbor radioed back and said he figured I got it started since he did not get another call.

I am posting this so that others that want to use mogas and have not, will remember to use caution when they make the change. I went into this experiment not knowing what would happen and had a plan for it not working. Had I had these issues sooner, the mogas would have been drained out and used in my zero turn mower. Mower runs well on the ethanol free mogas I have been feeding it for the past 3 years.
 
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That is very interesting. I never had any problems at all with Mogas. None. Zero. Ran it all the time in my Lycoming, not fuel injected.

Where I live, we have a more boutique fuel, with a higher mandated RVP year round. It is actually closer to 100LL. So vapor lock is not an issue.

With fuel injection, should not be a problem.
 
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interesting posts but you're playing with fire in my humble opinion. Vapor pressure and it's consequences are fuel system design considerations. More specifically, it is more typically a fuel pump suction side design consideration. If you haven't done the requisite system analysis and subsequent testing, you could easily turn yourself into a statistic. A change in blends, dirty pre-filter, etc. and what was previously good conditions for MoGas use suddenly isn't. Please use caution.
 
Winter fuel blend

I was using E0 91 octane in my carbed 0-320 with no problems for a couple hundred hours until I got a tankful of what i surmise to be winter fuel in May. Engine stalled and wouldnt start so i pushed it of to the side, pointed it into the wind and 25 minutes later was good to go. Kind of put me off using mogas though.
 
I was using E0 91 octane in my carbed 0-320 with no problems for a couple hundred hours until I got a tankful of what i surmise to be winter fuel in May. Engine stalled and wouldnt start so i pushed it of to the side, pointed it into the wind and 25 minutes later was good to go. Kind of put me off using mogas though.

Are you certain of the cause, or the exact nature of the problem. We never had any issues with our 0-320.
 
Its been couple years

But i think the airport manager suggested that was the cause. He didnt sell a lot and my tankfuls were probably leftover from winter. It never happened again and engine ran fine for the 50 mi trip home. But i did dilute it with 100ll asap.
 
I would not...

Have had vapor lock issues with 100LL on the ground in hot southern Kalifornia during initial flight testing with oil temperatures over 230.

According to your post, you had vapor lock issues with 100LL.

It takes very little to adapt a fuel system to deal with mogas but one of the most important parts of adapting your fuel system to burn
mogas is keeping your engine/oil and fuel system COOL.
There is no getting around the higher vapor pressure of mogas and using it in an airplane that exhibits vapor lock issues when using 100LL is asking for trouble.

91 E10 works just fine if your fuel system is designed to handle it.
Ethanol is an octane booster, pure ethanol rates at 112 Octane.
I have never once checked a fuel sample other than the customary water check we all do during pre flight, it works for me.
The higher vapor pressure of low octane gasoline allows for better atomization
and in my experience a more complete burn. In other words, when I fly on mogas, I am able to lean a full gallon lower than when I burn 100LL. There is no noticeable speed loss or temperature change.
My CHTs are in the 320-340 range on average days and oil temp is rock solid at 180 and lower during cold month when I close off the air supply.

I never really built my system to save money but rather to see if it can be done safely. Getting a break on $7.30 Avgas as of today is a bonus.
 
I was using E0 91 octane in my carbed 0-320 with no problems for a couple hundred hours until I got a tankful of what i surmise to be winter fuel in May. Engine stalled and wouldnt start so i pushed it of to the side, pointed it into the wind and 25 minutes later was good to go. Kind of put me off using mogas though.


Those seasonal transitions are problematic. Winter fuel in May is far from uncommon around here. I run into that with my tractor too…the convenience store where I buy diesel tends to be a little slow on the transition to summer blend fuel, and for my boats I have to be careful when I order a delivery of 91 octane no-ethanol for my storage tank….too early and I’ll get winter blend 91 octane. It’s part of the problem of what Lycoming refers to as “airworthiness” of the fuel we use in our airplanes. The fuel might meet the right specs (on paper) but the care of the fuel taken by the average gas station may not be up to aviation standards.
 
We have REC gas here in Michigan. I think it is 91. I have an O-320 D2A that is approved for mogas. The last of our $4.80 100LL ran out yesterday so we will be over $6 now.

Is there a reason I should not mix REC 93 with 100LL? Maybe 5 gal REC and 13gal 100LL? I know people with REC in one tank and 100LL in the other.

I am less concerned with saving the money - but interested in a cleaner engine and dont know if it is worth any possible issues.

I read this entire thread and I am more confused than ever.
 
Truck it

Here's how I get MOGAS to the airport. Ironically, the current 100LL price at my home airport is actually less than 91 octane pump gas nearby. And fuel price is my driver for hauling fuel. Prior to the last year, it was generally over a $1 a gallon more for avgas, so it's interesting times here is Wackifornia.
 

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I am less concerned with saving the money - but interested in a cleaner engine and dont know if it is worth any possible issues.

I read this entire thread and I am more confused than ever.
The reason that there is not a simple answer is that every engine and aircraft is different, and of course every pilot is different.

No one wants to go out and say "sure! Just use mogas - I do!" and then your fuel system does not support ethanol, and you have an engine failure at night, over the mountains. Then your widow's lawyer scours VAF and then finds someone to sue.

The safe thing is to use 100LL, and if you want to use something better for your engine, you will have to determine if your fuel system can handle it, that you understand the risks of vapor lock, that your compression ratios support slightly lower octane fuel, and that you know how to manage your engine in case things start going off the rails.

Simple answer: Use 100LL.
Longer answer: Wait for G100UL to arrive at your airport.
Crazy long answer: Spend hours reading everything you can on the internet, or get a buddy to do that for you, and then make a decision based on your exact engine/aircraft/experience/environment/risk tolerance.
 
Here's how I get MOGAS to the airport. Ironically, the current 100LL price at my home airport is actually less than 91 octane pump gas nearby. And fuel price is my driver for hauling fuel. Prior to the last year, it was generally over a $1 a gallon more for avgas, so it's interesting times here is Wackifornia.

It's the same thing in Wackytexas, non-ethanol 91 is more expensive than avgas in my area.
 
It's the same thing in Wackytexas, non-ethanol 91 is more expensive than avgas in my area.

This too shall pass…..

I just wish any airport in my area offered Swift 94. I keep banging my head against the wall with the FBOs and just get the stiff arm as they repeat the AOPA mantra “drop in replacement or nothing”. Considering the cost of 100LL, and the projected higher cost of 100UL, I suspect we are on the fast road to nothing.

I burn 25%-50% 93 ethanol free mogas when I can get it. The engine (normal compression IO-360-M1B) runs fine on this but the vapor issue is always hanging over my head. Swift 94 would be a much better fuel than 93 mogas or 100LL.

Carl
 
I remember putting over 1500 hours of mogas on a Robinson R22 helicopter back in the day. My next plane in a couple of months has a Lycoming TIO 540 TwinTurbo so sadly no more thoughts about any mogas options for me.
 
Swift Fuel Deleivered in FL.

@Carl.

My friend buys 94UL in bulk from a distributor here in FL. A reinforced 700 Gal.US tank is delivered to his property for ~15 - 20% more than the cheapest self serve around here; less than full serve at the larger FBOs. Something you may want to look at. The hardest thing is storing it legally and without objection. The airport FBOs obviously will fight such.

He's been using it exclusively in a Rotax for a few years now. It does burn as clean as advertised.

Edit = he just text’d me back. $5.55 gallon delivered.
 
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Thanks Gary for the info and for resurrecting this thread. Were you getting all the mogas from one source? I'm wondering if that was some or all of the cause of your issues, i.e. just some bad gas. From what I've read there can be a lot of variation in quality.

This topic intrigues me and I've considered similar experimentation with non- ethanol premium from a local station but lately the price is more than 100LL. Though cost is only part of it, I just wish I could get the lead out -- of my exhaust valves, and spark plugs, and the tailpipe.
 
Thanks Gary for the info and for resurrecting this thread. Were you getting all the mogas from one source? I'm wondering if that was some or all of the cause of your issues, i.e. just some bad gas. From what I've read there can be a lot of variation in quality.

This topic intrigues me and I've considered similar experimentation with non- ethanol premium from a local station but lately the price is more than 100LL. Though cost is only part of it, I just wish I could get the lead out -- of my exhaust valves, and spark plugs, and the tailpipe.

I only purchased mogas twice from the same retailer. They have been in business for more than 40-years and sell other petroleum products like heating oil from their own trucks.
 
I burned a 50/50 mixture of 100LL and 87 octane alcohol free gas for the last year with no problems. I store the fuel on my farm where I keep my plane. I saved very little money but it will give some options in the future. I would try a larger percentage of 87 mogas but I want to keep the octane up as my engine is 91 octane minimum.
 
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