How Does MoGas work?

Your RV can burn Mogas, I assume? What engine do you have?
 
Boat/farm/ATV gas is ethanol-free around here (BC, Canada). Cheaper, too, since highway taxes do not apply. It's premium unleaded.

Dan
 
zaitcev said:
I have an HKS-700E engine, so I fly on ethanol-free gasoline unless I am on a very long cross-country (unfortunately anything more than 150 nm for me is a very long cross-country). I get it from a local pure-gas station. Due to the distance to the pump and required fuel burn to transport the gas, there aren't any savings, but at least I reduce or eliminate lead.

The station is right next to a bigger airport and I hear that half the field fuels there (I suspect some do not bother with STC even). Their unleaded pure gas is rated (R+M)/2 91, so it goes into Rotaxes easily. I see a number of pilots driving pickup trucks with bed-mounted tanks and pumps.

Now it all is easy if you fly a CTLS that burns 4 gph at 5000 rpm cruise. Even easier for me: my cruise burn is 3.2-3.4 gph. There are limits to how much gasoline you can store and transport. You probably don't want to rely on a 5gal can if you have a twin.
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My CTLSi gets 3.5gph at 5200rpm 120KTAS cruise and burns 91E10 right out of the discount gas pumps. I don't store it in cans, I have a 60 gallon DOT approve steel transfer tank on a trailer. When traveling, I bring Decalin and scavenge out the lead from 100LL.
 
CTLSi said:
My CTLSi gets 3.5gph at 5200rpm 120KTAS cruise and burns 91E10 right out of the discount gas pumps. I don't store it in cans, I have a 60 gallon DOT approve steel transfer tank on a trailer. When traveling, I bring Decalin and scavenge out the lead from 100LL.
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If you can find alcohol free unleaded, you will improve your fuel economy.
 
CharlieTango said:
Both the Rotax and my airframe are approved for ethanol
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I wonder how they accomplished that. I was under the impression the main fear of ethanol gas is water retention and the high risk of it freezing at altitude.
 
Never heard about freezing... Doesn't seem to be an issue in cars...

The issue appears to be the rubber and similar components that are weakening damaged by the alcohol. The rubber tanks in bonanzs are a good example.
 
That is a concern but the water should still sump out since the ethanol/water blend is still heavier than gas and should drop to the bottom of the tank.

At least it drops to the bottom when I do an ethanol test in my "test tube-ish" rain gage.
 
Henning said:
If you can find alcohol free unleaded, you will improve your fuel economy.
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I need to improve 3.5gph at 120KTAS? And do what? Drive further to get the fuel, and pay more for it?

My gas is 1 mi from the airfield. And I am paying an avg of $3.60 for it. Flying for free would be the only way to improve on this model.
 
Grum.Man said:
I wonder how they accomplished that. I was under the impression the main fear of ethanol gas is water retention and the high risk of it freezing at altitude.
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If true, no one could drive a car... Mogas works just as well as avgas and a heck of a lot cheaper. And doesn't clog your engine with lead...
 
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timwinters said:
That is a concern but the water should still sump out since the ethanol/water blend is still heavier than gas and should drop to the bottom of the tank.

At least it drops to the bottom when I do an ethanol test in my "test tube-ish" rain gage.
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It is no more a concern than water in a tank full of 100LL. Mogas is the same as avgas sans lead. As long as you don't let your aircraft sit for 6 months between engine starts and outside you get the benefit of fresh fuel and no lead deposits.

The aircraft has to be designed to use it. That means building with the same rubber, silicon, calking and engine components autos use to deal with Ethanol.
 
CTLSi said:
I need to improve 3.5gph at 120KTAS? And do what? Drive further to get the fuel, and pay more for it?

My gas is 1 mi from the airfield. And I am paying an avg of $3.60 for it. Flying for free would be the only way to improve on this model.
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Geez. All he said was IF you could you could improve.
 
Greg Bockelman said:
Geez. All he said was IF you could you could improve.
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No. He said 'if i could find ethanol free mogas' i could improve. That's a false assumption.

Ethanol has no role in engine efficiency. It's a burden the green-goons have placed on fuels. Having to find Ethanol free gas costs more and is less convenient. Since I can burn Ethanol gas, I am able to get mogas cheaper and closer.
 
timwinters said:
You're well on the way to setting the new record for being wrong the most times in one thread. :rofl:

Keep going! I'm sure I'm not the only one enjoying the show. :popcorn:
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Just educating the public. Read and learn.
 
So what do you think he said wrong?

In my last four aircraft, Mogas WAS the same as avgas, sans the lead (and the absurd cost). Sure, you can go into all sorts of petrochemical engineering gibberish to explain the esoteric differences between the fuels, but operationally (which is all that matters to anyone in the real world) there was no difference.

Well, except that the engines ran better on mogas.

Water was no more of an issue with mogas than it was in a tank of 100 LL. And cold weather ops with ethanol laced mogas is not an issue with cars.

The only thing I'm unsure of is his statement about ethanol having "no role in engine efficiency".

So what did he get wrong?
 
CTLSi said:
Mogas is the same as avgas sans lead.
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The lead (tetraethyl lead) is there to inhibit detonation. Unleaded fuels are made differently to achieve the same thing without the lead. The base fuel is different chemically.

There used to be a guy that hung around the RAH forum. Dan Horton. He had a good post on it one time; he said that unleaded Mogas was made of long-chain molecules that resisted spontaneous combustion under heat and pressure, thereby reducing the risk of detonation. It was made under totally different processes in the refineries, which is what makes refineries hate making Avgas, which amounts to about 1% of gasoline production. I'm sure they'd love to get rid of the machinery that is useless for anything else.

Dan
 
Jay Honeck said:
Well, sorry, but my decade-plus experience with running mogas in aircraft doesn't support your assertions.
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What about the folks who got to replace their fuel tank bladders after using mogas?

mogas<>avgas and the difference in chemistry is important
 
Clark1961 said:
What about the folks who got to replace their fuel tank bladders after using mogas?

mogas<>avgas and the difference in chemistry is important
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They were probably worn out before the Mogas was even used. Without first hand knowledge I'd file that as OWT.


Been using 87 ethanol free Mogas all year in the wet winged 177, and on/off for 10 years. The smell and color is about the difference I've noticed.

I only buy at 15 to 30 gallons a shot at the local gas station and I test each load for ethanol contamination. I pump a gallon or two into my car in effort to clear any ethanol from the station's pump system before filling the test tube and then the gas cans.
 
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Clark1961 said:
What about the folks who got to replace their fuel tank bladders after using mogas?

mogas<>avgas and the difference in chemistry is important
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??? Never met one.

If they used ethanol contaminated mogas, I could see the bladders being ruined. Otherwise, mogas/avgas, same/same.
 
Jay Honeck said:
So what do you think he said wrong?

In my last four aircraft, Mogas WAS the same as avgas, sans the lead (and the absurd cost). Sure, you can go into all sorts of petrochemical engineering gibberish to explain the esoteric differences between the fuels, but operationally (which is all that matters to anyone in the real world) there was no difference.
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They work about the same in your engine, but the difference is more than just the added lead.

Water was no more of an issue with mogas than it was in a tank of 100 LL. And cold weather ops with ethanol laced mogas is not an issue with cars.
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Ever buy "dry gas"? Guess what is in it... The ethanol will actually make the fuel more water tolerant - up to the point that the water/ethanol separates from the gas - then you have a problem. But it's not a problem likely to occur in most aircraft.

The only thing I'm unsure of is his statement about ethanol having "no role in engine efficiency".
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That OH on the end of the molecule takes up a lot of room without giving back much energy. The heating value of ethanol is significantly lower than gasoline.


Dan Thomas said:
The lead (tetraethyl lead) is there to inhibit detonation. Unleaded fuels are made differently to achieve the same thing without the lead. The base fuel is different chemically.

There used to be a guy that hung around the RAH forum. Dan Horton. He had a good post on it one time; he said that unleaded Mogas was made of long-chain molecules that resisted spontaneous combustion under heat and pressure, thereby reducing the risk of detonation. It was made under totally different processes in the refineries, which is what makes refineries hate making Avgas, which amounts to about 1% of gasoline production. I'm sure they'd love to get rid of the machinery that is useless for anything else.

Dan
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Actually, you use tighter molecules like aromatics to improve resistance to abnormal combustion - the long straight chain paraffins tend to break down in the end gas region ahead of the flame front and result in knock. But, yes, the mix is different to get the same octane rating without the lead.
 
There is a ethanol free station close to the airport where I used to keep my STCed plane.

Even though it was ethanol free I still would test it by taking a small water bottle drinking all but about 1/8, filled it with gas, shook it, and verified the water to fuel separation level didn't go up. Worked well and the plane, which idled much better and ran great on mogas.

Easiest way to transport fuel IMO is in stainless steel 15.5gal kegs, they hold enough that you don't need a small army of containers, but are manageable to move without equipment, also tuff as nails.

90av45.jpg
 
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Clark1961 said:
mogas<>avgas and the difference in chemistry is important
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Don't confuse them with facts, Clark.

bnt83 said:
Without first hand knowledge I'd file that as OWT.
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Do you realize you're debating with someone in the petrochemical industry that knows just a little about what he says?

BTW...Brian, Jay, don't confuse my list of incorrect information spewed by CTLSi with an argument that ethanol free MoGas is bad in airplanes that have STCs to burn it. I burn it too and I doubt that Clark was referring to this either. The topic was ethanolized MoGas...
 
Grum.Man said:
I wonder how they accomplished that. I was under the impression the main fear of ethanol gas is water retention and the high risk of it freezing at altitude.
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If you read the STCs, the concern in the 70s was about vapor lock, not freezing.
 
The STC for our Cherokee 180 cost so much, that it would take over 30 years to begin to realise any kind of cost savings. So we didn't get it. With Dads 182, it was a couple hunnerd bucks, Logbook entry, and a sticker to be stuck by the fuel cap.
 
Ouch! 2900 bucks!

For mine it was something like 1.50 per hp. Of course it's jus paper work and no mods to the plane aside from new decals for the fuel caps.

http://www.autofuelstc.com/
 
Henning said:
You Bet! Get the lead out, there is nothing there that's good.

BTW, you can remove ethanol from gas by washing the gas with water and then running it through a water separating filter like a Racor and draining the water and alcohol off. The alcohol will abandon the gas and fuse to the water and then it's easy to remove. Cost a couple hundred to setup a nice rig that you can also use to pump the fuel up into the plane. You can build it all as well as your transport tank on a little flatbed trailer. Figure $2500 to build a decent rig that will assure you alcohol free MoGas and allow you to buy at bulk price from distributors before the gas station, store and pump it into the plane. You also get to pump it into your cars, so you actually have your own little gas station with rack price fuel.
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I heard that Ethanol is added at the terminal when it goes in the truck. If you can buy bulk gasoline, you should be able to buy it without ethanol in it.
 
The Ethanol is not the culprit. Lead is the culprit. Lead spoils everything in an engine including the oil.

The higher horsepower hybrid fuel engines like the Continental IO-360-AF can burn Mogas with Ethanol, they just need more octane. At least 93.

The Rotax 912 can burn 91E10, in fact it prefers it.
 
timwinters said:
Don't confuse them with facts, Clark.


Do you realize you're debating with someone in the petrochemical industry that knows just a little about what he says?

BTW...Brian, Jay, don't confuse my list of incorrect information spewed by CTLSi with an argument that ethanol free MoGas is bad in airplanes that have STCs to burn it. I burn it too and I doubt that Clark was referring to this either. The topic was ethanolized MoGas...
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Terms get too mixed up in discussion and then nothing meaningful happens.
 
timwinters said:
That is a concern but the water should still sump out since the ethanol/water blend is still heavier than gas and should drop to the bottom of the tank.

At least it drops to the bottom when I do an ethanol test in my "test tube-ish" rain gage.
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That is my experience. I roll it around a bit then just set it aside and wait a few minutes before making a determination.

I sump tanks well in the hangar which ends up in my car.
 
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Grum.Man said:
I wonder how they accomplished that. I was under the impression the main fear of ethanol gas is water retention and the high risk of it freezing at altitude.
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No, that's not an issue I was ever made aware of. The issues are of vapor pressure and vapor lock, and material compatibility with the synthetics in planes and the alcohol. There is also an issue with corrosion in aluminum. Never heard about water freezing, in fact, alcohol is used to prevent that.
 
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