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Mogas vs. 100LL?

TXFlyGuy

Well Known Member
Okay...certainly this has been beat to death on this forum. But I'm curious how many here actually burn 93 Octane pump gas in their RV's?

After reading more about the auto fuel here in North Texas, we have "reformulated fuel" year round. This has the benefit of cleaner burning, with a much lower RVP (7.8, close to 100LL of max 7.0) number making flying at altitude a non-issue.

We might just purchase one of the 58 gallon tanks, with a self contained fuel pump and carry it in the rear of my Explorer.

The fuel lines in use are alcohol resistant, and chemical resistant. So burning the E10 fuel is not a problem, and the auto engines we are using were designed to run on this.

The benefits of burning 93 Octane pump gas:

1. $2.80/gallon vs. $5.00/gallon for 100LL.
2. No lead, so your engine burns much cleaner.
3. Longer spark plug life.
4. Longer engine oil life.
5. No ugly exhaust smudge down the side of your cowling.

We found a good means of transporting fuel here:

https://www.walmart.com/ip/Emiliana-...BoCJZwQAvD_BwE
 
The link isn't working, anxious to see what you found at Wal-Mart to transport fuel inside your vehicle.
 
MoGas Vs 100LL

Okay...certainly this has been beat to death on this forum. But I'm curious how many here actually burn 93 Octane pump gas in their RV's?

After reading more about the auto fuel here in North Texas, we have "reformulated fuel" year round. This has the benefit of cleaner burning, with a much lower RVP (7.8, close to 100LL of max 7.0) number making flying at altitude a non-issue.

We might just purchase one of the 58 gallon tanks, with a self contained fuel pump and carry it in the rear of my Explorer.

The fuel lines in use are alcohol resistant, and chemical resistant. So burning the E10 fuel is not a problem, and the auto engines we are using were designed to run on this.

The benefits of burning 93 Octane pump gas:

1. $2.80/gallon vs. $5.00/gallon for 100LL.
2. No lead, so your engine burns much cleaner.
3. Longer spark plug life.
4. Longer engine oil life.
5. No ugly exhaust smudge down the side of your cowling.

We found a good means of transporting fuel here:

https://www.walmart.com/ip/Emiliana-...BoCJZwQAvD_BwE

I've been running only 93 Octane pump MoGas for the last five years. I only run 100LL when I don't have access to the MoGas. My RV-7A has an IO-360 8.5:1 compression engine.

Besides the need for ethanol compliant hoses (including the oil cooler hoses), What I have found is that there can be no 90* fittings from the engine mechanical pump back to the aux fuel pump. I have also added an independent fuel pressure sensing system that automatically turns on the aux pump if a low fuel pressure event occurs. This auto aux pump circuit can trigger on very hot summer days, or on initial steep climb outs on hot days. I have NEVER had an engine loss of power event.

All fuel related components must be ethanol compliant. The Lycoming fuel pump was the ONLY component that I couldn't get technical compliance for. But when searching for replacement fuel pumps (and their history) in countries that use ethanol based fuels (think Brazil) I found that they were not having issues with standard Lycoming fuel pumps. Nor have I after five years of using ethanol based fuel.

If I were to build another RV, I'd be putting a fuel pump in both tanks, and have a third aux pump as well. I would then remove the engine driven pump.
 
I've been running 91E10 for the last 350-ish hours, with occasional 100LL from a long cross-country. Engine is quite happy with it, but I've done considerable modification on the fuel system to keep the fuel cool and not boiling in the FWF area. I get excellent service now out here in hot west Texas weather, including flights into the lower flight levels. Highest I've been with it so far is FL230, but FL190 is realistically the highest reasonable altitude for normal use, anything more than that is just for bragging rights.

Double-firesleeved every fuel line FWF for insulation and heatshields near exhaust pipes
Removed engine driven fuel pump
Dual electric pumps (parallel for failure protection) through an Andair duplex valve
AFP purge valve installed for hot-start fuel pre-circulation to return hot fuel to the tanks before start
Changed to .022" orifices on the injectors (Gami) for better idling. This requires a higher fuel supply pressure for fuel-power flow, I'm running about 42 psig to the servo.

I'm buying at Sams club in a 125-gallon stainless tank with a 12vdc pump, just load it in the back of the pickup with a forklift and drop it back at the hangar. $2.47/gal a few weeks ago.
 
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What you haven?t mentioned is detonation resistance. 93 car gas is about 89 motor octane - quite a bit less than 100. With 8.5:1 pistons I?d think you?re pushing the limits. But without testing, I really don?t know.
 
I run 92 octane non-ethanol gas in my Sonerai. Granted, its only a 10gal tank. But, I wouldn't hesitate to cary 4 5 gal jugs of non-E for blending with 100LL in an RV when at home.

Below is what I carry my Non-E in, in the back seat floor pan of my Honda Accord. Fill to to exactly 5 gal, leave space for expansion, and cap them off good and snug. I don't have any gas fumes in the car at all.

https://www.amazon.com/VP-Gallon-Sq...argid=aud-801381245258:pla-617740825168&psc=1

Check out https://www.pure-gas.org for availability of non-E gas.
 
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With respect to detonation - I'm running 8.7:1 compression with piston oil squirters on my IO360, Superior forward facing induction and Bendix servo. During the hot summertime I can make the engine go into detonation by running LOP down low (below about 6000) and running just lean of peak during a hard climb - just about the worst case scenario - so I normally climb full ROP until that point then go WOTLOP and transition to cruise-climb at about 800 feet per minute and adjust mixture to keep my hottest cylinder (#4 for me) at or below 400F until level-off.

The key take-away here - detonation is a real thing and can happen with inferior fuels if you don't pay attention. Instrumentation is required, and thorough testing is desired.

EDIT - I've run some tanks of 93E10 as well - and have not experienced any detonation with that mix, though I didn't really try to find it either. Apparently the detonation margin curve runs out of headroom in the 91-93 octane region, and we are running very close to the edge.
 
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One potential problem with transporting gasoline in some of these larger tanks is that they are most likely not certified for gasoline. Federal hazmat regulations prohibit it. And most states go by the federal code, to my knowledge.

Although it may not necessarily be dangerous, if you get caught filling a tank that is only certified for combustibles (diesel, kerosene, etc.) by a fire marshal or DOT officer, it could be problematic.
 
I was just going to ask how long the E0 car gas stays ?fresh?? I use seafoam to stabilize the fuel in my beach cruiser truck which can go months between fill ups and never has any fuel issues but is it safe to use a stabilizer in a proper aircraft engine?

I ran 91E10 in a Rotax 912. 2 to 3 months between flights and never a problem. I used sea foam as well.
 
With respect to detonation - I'm running 8.7:1 compression with piston oil squirters on my IO360, Superior forward facing induction and Bendix servo. During the hot summertime I can make the engine go into detonation by running LOP down low (below about 6000) and running just lean of peak during a hard climb - just about the worst case scenario - so I normally climb full ROP until that point then go WOTLOP and transition to cruise-climb at about 800 feet per minute and adjust mixture to keep my hottest cylinder (#4 for me) at or below 400F until level-off.

The key take-away here - detonation is a real thing and can happen with inferior fuels if you don't pay attention. Instrumentation is required, and thorough testing is desired.

EDIT - I've run some tanks of 93E10 as well - and have not experienced any detonation with that mix, though I didn't really try to find it either. Apparently the detonation margin curve runs out of headroom in the 91-93 octane region, and we are running very close to the edge.

Hi Greg... question.... how do you detect detonation? Thanks
 
Hi Greg... question.... how do you detect detonation? Thanks

You can't hear it, you can't even really use a decent detonation detector on the engine due to all the mechanical noise on an air cooled engine. The way I look for it and detect it is watching my CHT's very closely when I'm operating close to the bears den. When you have a cylinder in the 400F region and it suddenly takes off climbing 1-2 degrees per second, it's almost certainly a detonation event. Time to do something NOW to stop it. Full rich, lower the manifold pressure, lower the nose to get some cooling air, or all of those. Once you've got a cylinder hot enough to detonate you'll create hot spots inside the combustion chamber that will keep it going, and lead to pre-ignition. That, in the famous words of Ricky Ricardo, is "bad bongos". Get back to a stable cool operating region and let the cylinder cool off, and then try again.

Caution is advised here - engine damage can occur very quickly when you get into detonation/pre-ignition operating ranges. This is not an area to play with unless you are prepared for dealing with the consequences. If you let the cylinder go from detonation to full pre-ignition, you can scrap a piston within a few seconds and be looking at a full engine rebuild.

I certainly would not recommend that others do what I am doing - you may have really good results running 93 octane, but wipe out your engine trying to run 91. I'm comfortable running mine on 91E10 but I won't let anyone else do it with my airplane. If someone else is going to be PIC in my airplane it will be running 100LL.
 
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That is part of the beauty of a non-standard engine, liquid cooled, with an ECU. Knock sensors / anti-detonation detection, can be set up to let you know what is happening.

But with the V8, being set to run on 92/93 Octane E10 pump gas, it should never really be a factor.
 
Okay...certainly this has been beat to death on this forum. But I'm curious how many here actually burn 93 Octane pump gas in their RV's?

After reading more about the auto fuel here in North Texas, we have "reformulated fuel" year round. This has the benefit of cleaner burning, with a much lower RVP (7.8, close to 100LL of max 7.0) number making flying at altitude a non-issue.

We might just purchase one of the 58 gallon tanks, with a self contained fuel pump and carry it in the rear of my Explorer.

The fuel lines in use are alcohol resistant, and chemical resistant. So burning the E10 fuel is not a problem, and the auto engines we are using were designed to run on this.



The benefits of burning 93 Octane pump gas:

1. $2.80/gallon vs. $5.00/gallon for 100LL.
2. No lead, so your engine burns much cleaner.
3. Longer spark plug life.
4. Longer engine oil life.
5. No ugly exhaust smudge down the side of your cowling.

We found a good means of transporting fuel here:

https://www.walmart.com/ip/Emiliana-...BoCJZwQAvD_BwE


Ive been burning 91 octane ethanol free fuel mixed with 100LL mix for 5 years now in my YIO-360-M1B. The only problem noticed is mag drop higher than normal (>125rpm) on hot days
 
I run 91UL almost exclusively for daily use. But when I travel, I burn 100LL with Decalin.

Looking at the price of the tank from Walmart at about $871, you can get an actual DOT approved gas tank from www.attatank.com for your truck bed, which is what I did. Including the pump it was about $1300. However, at about 200 hours a year at 5 gallons per hour, the payback is pretty quick. You can haul up to 119 gallons.

Additionally, here is Wackifornia, you can file to refund the road taxes at 58? a gallon annually, so if I burn 1000 gallons, I can get $580 back annually. That alone pays for the tank within a couple years; sooner if you're burning more, which I assume most folks are in the 8-12 gph range.

Also, regarding the difference between a diesel only and gas tank, keep in mind that you need a static line for diesel; the big difference is that the tanks for "diesel only" are generally not certified for gasoline. Additionally, if you're running gas with ethanol, the pump seals should be viton, which they may not be in a diesel only pump. Other than that, it's just a tank.
 
Detonation detection, thanks for the explanation.

You can't hear it, you can't even really use a decent detonation detector on the engine due to all the mechanical noise on an air cooled engine. The way I look for it and detect it is watching my CHT's very closely when I'm operating close to the bears den. When you have a cylinder in the 400F region and it suddenly takes off climbing 1-2 degrees per second, it's almost certainly a detonation event. Time to do something NOW to stop it. Full rich, lower the manifold pressure, lower the nose to get some cooling air, or all of those. Once you've got a cylinder hot enough to detonate you'll create hot spots inside the combustion chamber that will keep it going, and lead to pre-ignition. That, in the famous words of Ricky Ricardo, is "bad bongos". Get back to a stable cool operating region and let the cylinder cool off, and then try again.

Caution is advised here - engine damage can occur very quickly when you get into detonation/pre-ignition operating ranges. This is not an area to play with unless you are prepared for dealing with the consequences. If you let the cylinder go from detonation to full pre-ignition, you can scrap a piston within a few seconds and be looking at a full engine rebuild.

I certainly would not recommend that others do what I am doing - you may have really good results running 93 octane, but wipe out your engine trying to run 91. I'm comfortable running mine on 91E10 but I won't let anyone else do it with my airplane. If someone else is going to be PIC in my airplane it will be running 100LL.

Thanks Greg for the explanation of detonation detection!
 
I run 91UL almost exclusively for daily use. But when I travel, I burn 100LL with Decalin.

Looking at the price of the tank from Walmart at about $871, you can get an actual DOT approved gas tank from www.attatank.com for your truck bed, which is what I did. Including the pump it was about $1300. However, at about 200 hours a year at 5 gallons per hour, the payback is pretty quick. You can haul up to 119 gallons.

Additionally, here is Wackifornia, you can file to refund the road taxes at 58? a gallon annually, so if I burn 1000 gallons, I can get $580 back annually. That alone pays for the tank within a couple years; sooner if you're burning more, which I assume most folks are in the 8-12 gph range.

Also, regarding the difference between a diesel only and gas tank, keep in mind that you need a static line for diesel; the big difference is that the tanks for "diesel only" are generally not certified for gasoline. Additionally, if you're running gas with ethanol, the pump seals should be viton, which they may not be in a diesel only pump. Other than that, it's just a tank.

Thank you! Those tank people are in Cow Town (Fort Worth), just down the road from me. Just spoke with them, and they have exactly what I need.
 
Detonation

What you haven?t mentioned is detonation resistance. 93 car gas is about 89 motor octane - quite a bit less than 100. With 8.5:1 pistons I?d think you?re pushing the limits. But without testing, I really don?t know.

Detonation issues are resolved by proper timing. I've got duel PMAGs with an EI Commander, and am essentially running the PMAG "B" curve with an upper limit on the max advancement. The result is higher EGTs, and lower CHTs, and no detonation issues.
 
Thank you! Those tank people are in Cow Town (Fort Worth), just down the road from me. Just spoke with them, and they have exactly what I need.

Glad to help! BTW, you might say I referred them...they also offer military discount.
 
fwiw, i just e mailed the company that displayed the transfer tank on wheels as osh and they said fed regs kick over 119 gallons, not 95.
 
I have been running reg car gas in left tank for cruise flight, 50/50 mix in right tank for take off and landing for more years that I can remember. No mods on O-360. MMO added to fuel and some oil changes.
 
I have been running reg car gas in left tank for cruise flight, 50/50 mix in right tank for take off and landing for more years that I can remember. No mods on O-360. MMO added to fuel and some oil changes.

... and thank you for opening the secret for me 8 years ago :)


 
The way I look for it and detect it is watching my CHT's very closely when I'm operating close to the bears den. When you have a cylinder in the 400F region and it suddenly takes off climbing 1-2 degrees per second, it's almost certainly a detonation event. Time to do something NOW to stop it.

I've gotten the 390 into detonation with an ignition setting error, and Greg's description of the indication is accurate. When the CHT numbers suddenly start rolling like the gallons on a gas pump, it's time to make a change.

Although caution is warranted, test engines are routinely pushed into detonation on the dyno, over and over and over, and it doesn't hurt them. For certification, the FAA recognizes detonation comes in various degrees of severity. A minute of low to moderate detonation probably won't hurt anything. Sitting there brain dead while a cylinder or two is racing past 500F is another thing.

Detonation issues are resolved by proper timing. I've got duel PMAGs with an EI Commander, and am essentially running the PMAG "B" curve with an upper limit on the max advancement. The result is higher EGTs, and lower CHTs, and no detonation issues.

You mean "A" curve, with jumper between terminals 2 and 3, base near 20 BTDC, max advance 34 degrees?

Or "B", no jumper, roughly 25 base, but using the EI Commander to limit maximum advance to something less than the B's standard 39 BTDC? If so, what max are you using?

Higher EGT and lower CHT is typical for less advance. All good.
 
Although caution is warranted, test engines are routinely pushed into detonation on the dyno, over and over and over, and it doesn't hurt them. For certification, the FAA recognizes detonation comes in various degrees of severity. A minute of low to moderate detonation probably won't hurt anything. Sitting there brain dead while a cylinder or two is racing past 500F is another thing.

Agreed on all points. I'm pretty sensitive to the needs of the engine - I can count on both hands (without using my feet) the number of times a cylinder has exceeded 425F, and I've never had one above 440F. When a test engine on the dyno fails, it lets the smoke out of the engine. When the test engine in my airplane fails, it might let the smoke out of ME.
 
I run 91 alcohol free in one tank and 100LL in the other tank. I take off and land in the expensive stuff, then enroute I fly the cheap stuff. My airplane has never stumbled even once. I don?t let it sit for a long time. If my plane is going to sit for more than a month... 100LL all the way.

T
 
If you have a pickup truck, just get a clean 55 gallon drum and paint it red.
Use a siphon to decant it to your low wing RV, like the Safety Siphon or Siphon Pro. Secure the barrel so it doesn't slide around, and make up a ground wire with alligator clips for the drum and airplane.
Cheap, Easy, and handy to remove from your truck so you can use it for everything else a pickup does.
 
I used to run premium auto fuel in mine a few years back until one of my fuel injectors got closed off with some goop that I attributed to auto fuel additives. This was when I had two magnetos.

Last fall I loaded one tank with mogas for kicks... I?m now running dual electronic ignition and couldn?t for the life of me get it to run LOP without serious temp issues. I?m fine with 100LL thank you. No injector issues either.
 
Last fall I loaded one tank with mogas for kicks... I?m now running dual electronic ignition and couldn?t for the life of me get it to run LOP without serious temp issues. I?m fine with 100LL thank you. No injector issues either.

That's most likely a timing issue - you'll need to back off the advance a bit with lower octane fuels.
 
I was told that 93 Octane pump gas actually burns hotter, and has more energy than 100LL.

We will program our ECU Fuel MAP for 93, knowing that when we burn avgas it will be a little richer.

Also, without the lead, we will run full synthetic oil, Shell Rotella T-6.
 
That's most likely a timing issue - you'll need to back off the advance a bit with lower octane fuels.

Ditto.

Don't confuse how the spark is generated (coil control via a solid state switch rather than contact points) with the commonly too advanced timing schedules supplied by ignition vendors.
 
93UL car gas, 450+ hours

93UL in the right tank used for local flying and short CC. 100LL in the left tank used for landing, helps on hot starts. No mods, no issues in 4 years / 450 hours.
 
Mogas

I operate an RV10 IO540. It has 8.5 to 1 compression pistons. Would it be beneficial to put in 7 to 1 pistons at top overhaul for operations on mogas?
 
I operate an RV10 IO540. It has 8.5 to 1 compression pistons. Would it be beneficial to put in 7 to 1 pistons at top overhaul for operations on mogas?

My engine has 10.8-1 compression cylinders, and it is certified to burn 92 Octane fuel.

But it is liquid cooled. So that may be the difference.
 
I operate an RV10 IO540. It has 8.5 to 1 compression pistons. Would it be beneficial to put in 7 to 1 pistons at top overhaul for operations on mogas?

If you want to do it by the book, all is detailed in the table below:
https://www.lycoming.com/sites/default/files/SI1070AA Specified Fuels.pdf

You will be fine if you are running high octane mogas, but if you want to run regular, according to the book you need to have the lower compression pistons. That's the beauty of this document. There's no need to speculate or listen to sob stories telling you that it's not possible, as it's all clearly stated. I think you will find that you are better off keeping the standard compression pistons and sticking with the high octane mogas, as your efficiency will reduce as you go to the lower compression ratio. David Brown has posted a chart on the forum previously clarifying this (I can't find the link at the moment) and it is not an insignificant efficiency reduction with the lower compression.
I and many others, run RON98 (Super 98) high octane (about MON91, AKI93) in an 8.5:1 IO360-M1B, as the Lycoming table stipulates, and it works amazingly well LOP and ROP. I saw no difference in my temperatures compared to running Avgas and haven't run any since my first few hours of break-in. The most important thing is that you make sure your fuel system is set up correctly to reduce any chances of vapor lock, as there may be more variability in the Reid vapor pressure of the fuels you purchase, but nothing a properly designed system can't handle. Lycoming provides the approval for the engine to run on the low octane fuel, but in the kit world we don't have STC's, so it's up to the individual builder/owner to ensure suitability of the fuel system. As has been stated before, no tight right angle bends should exist in the fuel system, make sure your lines are properly shielded from radiant heat sources (exhaust) and insulated forward of the firewall (which they should be anyway). There's heaps of info on the forum regarding this, and none of it's that difficult. Once you start running mogas you'll be wondering why for so many years you were unnecessarily squirting lead into the atmosphere making everyone as dumb as rocks and burning $$ bills you didn't need to. The next step is an all electric conversion for your RV, so none of this will be a problem in the future. Bring on the end to burning those liquified dinosaurs and my continued unintended funding of a small number of extremely rich people in the middle east.

Tom.
RV-7
IO-360M1B (until electric is available)
 
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If you want to do it by the book, all is detailed in the table below:
https://www.lycoming.com/sites/default/files/SI1070AA Specified Fuels.pdf

You will be fine if you are running high octane mogas, but if you want to run regular, according to the book you need to have the lower compression pistons. That's the beauty of this document. There's no need to speculate or listen to sob stories telling you that it's not possible, as it's all clearly stated. I think you will find that you are better off keeping the standard compression pistons and sticking with the high octane mogas, as your efficiency will reduce as you go to the lower compression ratio. David Brown has posted a chart on the forum previously clarifying this (I can't find the link at the moment) and it is not an insignificant efficiency reduction with the lower compression.
I and many others, run RON98 (Super 98) high octane (about MON91, AKI93) in an 8.5:1 IO360-M1B, as the Lycoming table stipulates, and it works amazingly well LOP and ROP. I saw no difference in my temperatures compared to running Avgas and haven't run any since my first few hours of break-in. The most important thing is that you make sure your fuel system is set up correctly to reduce any chances of vapor lock, as there may be more variability in the Reid vapor pressure of the fuels you purchase, but nothing a properly designed system can't handle. Lycoming provides the approval for the engine to run on the low octane fuel, but in the kit world we don't have STC's, so it's up to the individual builder/owner to ensure suitability of the fuel system. As has been stated before, no tight right angle bends should exist in the fuel system, make sure your lines are properly shielded from radiant heat sources (exhaust) and insulated forward of the firewall (which they should be anyway). There's heaps of info on the forum regarding this, and none of it's that difficult. Once you start running mogas you'll be wondering why for so many years you were unnecessarily squirting lead into the atmosphere making everyone as dumb as rocks and burning $$ bills you didn't need to. The next step is an all electric conversion for your RV, so none of this will be a problem in the future. Bring on the end to burning those liquified dinosaurs and my continued unintended funding of a small number of extremely rich people in the middle east.

Tom.
RV-7
IO-360M1B (until electric is available)


An EP RV? I hope they invent a pill that doubles our lifespan cause you'll be using hydrocarbon Fuels for a looooooooooong time yet!:D
 
The previous owner/builder flew my plane for 400+ hours with 100LL in the right tank for takeoff and landings and 82 non-ethanol in the left tank for when he’s in cruise.

I’ve been doing the same but using 91 non-ethanol. I’ve done touch and goes on 91 with no issues except twice already if I land on 91 and shut down when I go to start it has a crazy misfire until I suppose the fuel lines get full of fuel (about 15 seconds) then it settles down to a smooth idle as normal.

Lately prices for 100LL are about the same as 91 non-ethanol so I don’t mess with it just to save $4 or $5 per tank load.
 
The previous owner/builder flew my plane for 400+ hours with 100LL in the right tank for takeoff and landings and 82 non-ethanol in the left tank for when he’s in cruise.

I’ve been doing the same but using 91 non-ethanol. I’ve done touch and goes on 91 with no issues except twice already if I land on 91 and shut down when I go to start it has a crazy misfire until I suppose the fuel lines get full of fuel (about 15 seconds) then it settles down to a smooth idle as normal.

Lately prices for 100LL are about the same as 91 non-ethanol so I don’t mess with it just to save $4 or $5 per tank load.

After the state tax rebate, 93UL is $2.39/gallon. Avgas here is $4.25-$4.50/gallon.

Burned 89 Octane pump gas in my C-172 for hundreds and hundreds of hours. Not only did the engine run so much better, but we saved $$$ on the gas!

We are not concerned about Ethanol, as our fuel line and tank sealant is chemical/alcohol tolerant.
 
We can only dream of fuel being that cheap!
Avgas can be around $12 gallon in the more remote places outback!
I run a 25% 98 'shandy' in the cooler months, engines runs just fine:)
 
It's not just a cost issue, but the big factor for us is the engine was designed to burn 93UL fuel.
Much cleaner, longer life oil and plugs too.
 
The benefits of burning 93 Octane pump gas:

1. $2.80/gallon vs. $5.00/gallon for 100LL. [False Econ when your engine flames out due to vapor lock]
2. No lead, so your engine burns much cleaner. [Lead increases Octane and Lubrication]
3. Longer spark plug life. [No, Lead can be cleaned from plugs with pick, blast good to go]
4. Longer engine oil life. [Doubt that (without data) especially if flame out due to vapor lock and forced landing is less than successful]
5. No ugly exhaust smudge down the side of your cowling.[You will not eliminate streaks from oil or exhaust]

We found a good means of transporting fuel here:
Avgas has a lower and more uniform vapor pressure than automotive gasoline so it remains in the liquid state despite the reduced atmospheric pressure at high altitude, thus preventing vapor lock

Only for LOW compression engines and need to have excellent cooling to avoid vapor lock. STC for Motor-Gas still results in vapor lock issue. When I say vapor lock I mean engine stops running. RV cowls are compact and hot.

Ethanol and Alcohol can cause swelling of seals in fuel system and loss of power.
 
Well...trying to remember the last time we had vapor lock with a fuel injected engine...never is the answer.

We run Reformulated Gasoline here year round. The RVP is maxed at 7.8. For 100LL, the max allowed is 7.0, although the numbers I see more often are in the 5.0 to 6.0 range.

My engine was designed for lead free gas. It will burn cleaner, so longer life oil and plugs is just a fringe benefit.

If there is oil streaking down my fuselage, it will be due to an oil leak. If there is an exhaust smudge on the cowling, the mixture is overly rich.

My C-172 ran for 100's and 100's of hours, all the way up to the low teens on 89 Octane pump (auto) gas. Vapor lock? Never.

I guess I have just been lucky? Maybe all those who burn mogas in their RV's are just lucky too? I honestly don't know.

edit: I do have a friend who likes burning the dreaded-leaded, simply because that is the only way he gets that "50 Mission" exhaust stain, just like a real P-51.
 
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Avgas has a lower and more uniform vapor pressure than automotive gasoline so it remains in the liquid state despite the reduced atmospheric pressure at high altitude, thus preventing vapor lock

Only for LOW compression engines and need to have excellent cooling to avoid vapor lock. STC for Motor-Gas still results in vapor lock issue. When I say vapor lock I mean engine stops running. RV cowls are compact and hot.

Ethanol and Alcohol can cause swelling of seals in fuel system and loss of power.

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.
 
High Wing

Well...trying to remember the last time we had vapor lock with a fuel injected engine...never is the answer.

We run Reformulated Gasoline here year round. The RVP is maxed at 7.8. For 100LL, the max allowed is 7.0, although the numbers I see more often are in the 5.0 to 6.0 range.

My engine was designed for lead free gas. It will burn cleaner, so longer life oil and plugs is just a fringe benefit.

If there is oil streaking down my fuselage, it will be due to an oil leak. If there is an exhaust smudge on the cowling, the mixture is overly rich.

My C-172 ran for 100's and 100's of hours, all the way up to the low teens on 89 Octane pump (auto) gas. Vapor lock? Never.

I guess I have just been lucky? Maybe all those who burn mogas in their RV's are just lucky too? I honestly don't know.

edit: I do have a friend who likes burning the dreaded-leaded, simply because that is the only way he gets that "50 Mission" exhaust stain, just like a real P-51.

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
 
Avgas has a lower and more uniform vapor pressure than automotive gasoline so it remains in the liquid state despite the reduced atmospheric pressure at high altitude, thus preventing vapor lock

Only for LOW compression engines and need to have excellent cooling to avoid vapor lock. STC for Motor-Gas still results in vapor lock issue. When I say vapor lock I mean engine stops running. RV cowls are compact and hot.

Ethanol and Alcohol can cause swelling of seals in fuel system and loss of power.

Adding just a small amount of AvGas to MoGas will change the specific-gravity of the mixture which will lower the vapor pressures quite a bit. As an example, a 90/10 (MoGas/AvGas) blend will bring the total vapor pressure down very close to the vapor pressure as pure AvGas.
 
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