earl72
Pre-Flight
i have a cessna 150 that has the auto gas stc done but am wondering what the performance difference is and some advice on using auto gas
auto gas vs av gas
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denverpilot
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First you'll need a source of non-ethanol added mogas. If it has ethanol added, you can't use it on any of the STCs that are out there for the C-150.
Would also recommend filling only one tank with it at first, that way you can see how your engine behaves on it. Shouldn't be any problem but have a tank of 100LL only available the first flight. Your other tank will probably be a "mix" of 100LL and mogas anyway that first time unless you ran it way down. Someone suggested it to me so I'm passing that advice along. It was a non-issue in our airplane but good advice nevertheless.
Generally it just works fine. The lower octane rating means a bit less bang for the buck in my tests in our C-182P. Slightly less power/speed at high altitudes. Just a few knots.
We recently found a bulk supplier of 91 octane mogas who'll sell to the public. Lugging it to the airport eats up in time, what you could have spent flying with 100LL.
Finding it at airports is very hit or miss. Websites are often wrong and don't track it well. Phone calls to the FBO get the best information still.
And I always do the "add water and shake" test before putting it in the airplane, checking for ethanol. Google that technique. EAA also makes a tester, but the water test works fine.
It's only a $1/gal difference here between our bulk supplier and the self-serve 100LL at the airport, but it adds up if you have ready access to it.
Ask car racers where they get their high octane stuff. This particular local bulk supplier does a brisk business with the race crowd for the super high octane stuff, I hear. They're only open M-F 8-5.
Would also recommend filling only one tank with it at first, that way you can see how your engine behaves on it. Shouldn't be any problem but have a tank of 100LL only available the first flight. Your other tank will probably be a "mix" of 100LL and mogas anyway that first time unless you ran it way down. Someone suggested it to me so I'm passing that advice along. It was a non-issue in our airplane but good advice nevertheless.
Generally it just works fine. The lower octane rating means a bit less bang for the buck in my tests in our C-182P. Slightly less power/speed at high altitudes. Just a few knots.
We recently found a bulk supplier of 91 octane mogas who'll sell to the public. Lugging it to the airport eats up in time, what you could have spent flying with 100LL.
Finding it at airports is very hit or miss. Websites are often wrong and don't track it well. Phone calls to the FBO get the best information still.
And I always do the "add water and shake" test before putting it in the airplane, checking for ethanol. Google that technique. EAA also makes a tester, but the water test works fine.
It's only a $1/gal difference here between our bulk supplier and the self-serve 100LL at the airport, but it adds up if you have ready access to it.
Ask car racers where they get their high octane stuff. This particular local bulk supplier does a brisk business with the race crowd for the super high octane stuff, I hear. They're only open M-F 8-5.
Greg Bockelman
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FYI, in a 150, it is all or none. Fuel feeds from both tanks at the same time. There is no left or right fuel valve position.
And there really is no discernible performance difference that I have ever been able to tell.
And there really is no discernible performance difference that I have ever been able to tell.
MSPAviator
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I've flown a C-152 with mogas. There is no performance difference I could tell. Not at full throttle and not during engine leaning. I lean aggressively for taxi (engine will sputter and die if I go full throttle), go full rich for takeoff, and start slowly leaning at about 500ft. AGL.
At the airport pump, mogas was $4/gal, 100LL was $5.26, that was a huge COST difference.
I don't think the low compression O-235 really needs 100 octane...
At the airport pump, mogas was $4/gal, 100LL was $5.26, that was a huge COST difference.
I don't think the low compression O-235 really needs 100 octane...
i have a cessna 150 that has the auto gas stc done but am wondering what the performance difference is and some advice on using auto gas
If you can find ethanol free mogas (if you have a marina in the area, find out their supplier) your engine will appreciate you using it. Much much cleaner burning. You may have to make your own fueling rig though, but that should pay for itself reasonably quickly at $2+ per gallon.
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I used to have a Cessna 150 and it actually ran better on auto fuel. At the time only 100/130 was available and that had a way too much lead for the O-200. One negative with auto fuel is that it deteriorates faster than aviation fuel.
dmccormack
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The Chief runs find on pure mogas -- I use about 25% 100LL, rest Mogas most of the time (not an exact mixture EXCEPT in the winter).
Car gas is not as stable and doesn't do well sitting for weeks at a time. Winters I run straight 100 LL.
Car gas is not as stable and doesn't do well sitting for weeks at a time. Winters I run straight 100 LL.
Dan Thomas
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Mogas gives the same power as Avgas. Octane rating has nothing to do with power output. Octane rating defines the fuel's resistance to detonation. A higher-compression engine needs a higher octane-rated fuel so it will burn without detonating; a low-compression engine like the O-200 will see no difference.
The O-200 really doesn't care for Mogas, in our experience. We had more trouble with valve guide and seat wear. The lead in the Avgas lubricates both guides and seats, but the high lead content of the 100LL fouls the plugs far sooner than the 80 that the engine was designed for. Four times the lead in 100LL as in 80.
Dan
The O-200 really doesn't care for Mogas, in our experience. We had more trouble with valve guide and seat wear. The lead in the Avgas lubricates both guides and seats, but the high lead content of the 100LL fouls the plugs far sooner than the 80 that the engine was designed for. Four times the lead in 100LL as in 80.
Dan
Jay Honeck
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I have run over 12,000 gallons of mogas through three different airplanes -- an Ercoupe, a Warrior, and a Pathfinder. I've run it at -20 degrees, and I've run it at +104 degrees. I've run it at sea level, all the way to 13,000 feet.
The only difference between mogas and avgas was a price differential of $1 to $2 per gallon in your pocket, and a MUCH cleaner engine. Most of our engines were NEVER designed to run on 100LL, which has 4 times more lead in it than the old (now unavailable) 80 octane fuel did. As a result, our current avgas is actually detrimental to our old-fashioned engines.
Sadly, I can no longer obtain unpolluted mogas where I live. If you can, use it while you can!
The only difference between mogas and avgas was a price differential of $1 to $2 per gallon in your pocket, and a MUCH cleaner engine. Most of our engines were NEVER designed to run on 100LL, which has 4 times more lead in it than the old (now unavailable) 80 octane fuel did. As a result, our current avgas is actually detrimental to our old-fashioned engines.
Sadly, I can no longer obtain unpolluted mogas where I live. If you can, use it while you can!
Tom-D
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Look for the date the auto gas STC s were issued to EAA and Petersen, you'll see at that time there was lead in auto fuel, only it was much less than 100/130 or 100LL. and so the 0-200 ran fine on it because the 0-200 and many other engines were certified on 80/87. auto fuel at that time was closer to the 80/87 than 100/130 or 100LL.
But in the years since then the lead was removed from auto gas and two chemicals were used to replace it as the burn rate retardant, they are toluene and benzene, neither has the BTU content of white fuel stocks, so the result was a reduction in power per pound of fuel. thus out cars and aircraft lost fuel mileage, plus the addition of alcohol will further lessen the BTU per pound of auto fuels.
Think about this, the EPA removed a tiny amount of TEL, and added 10% of toluene, and 10% benzene, now we only have 80% white fuel stocks, now add another 10% alcohol see why the FAA is reluctant to certify it.
I've always said the use of auto fuels in aircraft is simply a different set of problems.
the use of benzene in fuel attacks the rubber products that are of the older rubber compounds, it damages the inner lining of hoses, fuel cells and some carb parts.
the lead in 100LL burns but the lead does not, so it forms a soft deposit on any thing it sticks to. auto fuels burn leaving a hard carbon product, causing wear that the soft carbon products of 100LL does not.
MBDiagMan
Final Approach
There is no more energy per gallon in 100LL than any other octane. Where the octane rating comes in is allowing higher compression ratios and more advanced timing without spark knock. If the timing is adjusted to take advantage of higher octane fuel, then more energy can be delivered by the engine.
If no timing changes are made and either fuel can be used without spark knock, then the power delivered will be the same.
Doc
If no timing changes are made and either fuel can be used without spark knock, then the power delivered will be the same.
Doc
Personally, I don't see the need for 100LL at all if you don't always need it, but I would think that by using the stability of fuel issue, I would use 100LL in the summer and MoGas in the winter unless you're saying that you store it most of the winter, then I get it, but still don't think it's necessary if it's cold. Just park it with minimum fuel and then top off fresh when you go to use it. Do a prolonged taxi and run up.
dmccormack
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I fly less in the winter, so the fuel sits in the tanks for possibly weeks at a time.
Good article: http://www.eaa.org/autofuel/autogas/articles/1Autogas vs Avgas.pdf
kgruber
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Baloney!
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My "own fueling rig" is five gallon METAL safety cans downloaded to four gallons for ease of pouring through a Mr. Funnel.
Alaska Bushwheels has a very nice collapsable five gallon fuel bag for sale, but it is pricey. Lay it on the wing and the fuel pours itself.
There are other and cheaper bladder solutions that you can use along with a pump to pump the fuel up. I've had 2 back surgeries, fueling from 5 gallon jugs and slinging bladders on top of wings is not in my near future.
denverpilot
Tied Down
Tom covered the lower power thing. Sorry, I know octane is not a power rating and knew there was something wrong with that post when I was typing it, but it was late.
Rephrased: "Whatever's in our clean non-ethanol mogas we've used, it has less bang for the buck. The airspeed indicator does not lie. But it's not a huge difference."
Better?
Rephrased: "Whatever's in our clean non-ethanol mogas we've used, it has less bang for the buck. The airspeed indicator does not lie. But it's not a huge difference."
Better?
Tom covered the lower power thing. Sorry, I know octane is not a power rating and knew there was something wrong with that post when I was typing it, but it was late.
Rephrased: "Whatever's in our clean non-ethanol mogas we've used, it has less bang for the buck. The airspeed indicator does not lie. But it's not a huge difference."
Better?
Chemistry doesn't much lie either. I used to use it in 985s and 1340s with no degrade in performance and a lot less plug, valve and head problems.
Tom-D
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I have a hard time believing that too, or you are 1 in a million. the carbon built up on the valve stems is a very hard carbon that will wear the guides much faster than leaded fuels, Valves won't stick, simply because the carbon wears the guide away.
you may not pay at the pump, but you'll pay at overhaul..
MBDiagMan
Final Approach
Tom covered the lower power thing. Sorry, I know octane is not a power rating and knew there was something wrong with that post when I was typing it, but it was late.
Rephrased: "Whatever's in our clean non-ethanol mogas we've used, it has less bang for the buck. The airspeed indicator does not lie. But it's not a huge difference."
Better?
Your proof that YOUR engine develops less power on the lower octane gas indicates that YOUR engine requires higher octane fuel for maximum efficiency. Possibly due to ignition timing.
Doc
denverpilot
Tied Down
Yep, and that's what I was giving him... my operating experience with it so far.
But as Tom pointed out, it's not really a matter of octane, it's a matter of the make-up of the fuel that gets it up to 91... the feedstock is quite a bit lower than that.
In his C-150 with the O-200, I bet the OP can't tell the difference.
Just sharing my experience with our engine.A good friend runs MoGas in his C-150 in PHX whenever he can get it. No performance difference, but their MoGas used to be ethanol-added half of the year, and recently went to year-round, so he can't get it as readily now.
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Octane has nothing to do with BTU per pound of fuel.
In fact the higher Oct alcohol fuels have less BTUs per pound of fuel.
Remember instant heat (BTUs)causes detonation, less heat, less detonation. = higher Oct rating.
Dan Thomas
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The 150's O-200-A is certified for 80 octane fuel. Try to find any Mogas that has such a low octane rating. If he was getting less power because the engine needed a higher octane fuel, he would be getting detonation in his engine (unlikely due to the mogas' octane level) and the cylinder head temps would rise very sharply. The engine would not last long.
Raising octane rating does not raise power.
From http://en.wikipedia.org/wiki/Octane_rating
we read:
"Octane rating does not relate to the energy content of the fuel (see heating value). It is only a measure of the fuel's tendency to burn in a controlled manner, rather than exploding in an uncontrolled manner. Where the octane number is raised by blending in ethanol, energy content per volume is reduced."
Dan
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It doesn't make a hoot how lean you are, when you burn a fuel that will make a hard carbon it will cost you at overhaul.
Tom-D
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Just for us who are dummer than a _______ a BTU is the amount of energy that it requires to raise 1 CC of water 1 degree,,,,,,,,,, that's energy.
it's a known fact that alcohol has less BUTs per pound than white fuel stock.
we must know that during the Cat. cracking process the lighter distillates com off the top of the tower. those with the most BTUs come off the bottom. starting with heavy bunker oil at the bottom and benzene near the top with toluene just below.
What we need to know is simple, auto fuels in aircraft engines is not a cure all for the problems of burning a hydrocarbon fuel. the three major chemicals in auto fuel are white fuel stock, benzene, and toluene, each has it own specific gravity, and when stored in a tank and allowed to set, they will separate, so 3 weeks pass and you start the engine on white fuel stock with no burn rate retardant in it.
know why it is a know fact that you never allow auto fuel to set a lomg time? guess why? somebody busted their butt with it.
A few hundred dollars in valve guides over 1000+hrs of saving $2+gallon on average 40 or 55 GPH? Yeah, that's a good trade. If I simply errode the valve guide over the life of the engine, that is good value as it's not likely to cause a catastrophic failure. The hard carbon will polish as it wears the guide. Better than that sludge mix of lead and carbon that hangs valves open and causes the burnt valves.
Tom-D
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Valves and guides aren't the only place carbon collects. Piston ring grooves collect carbon too, and accelerate cylinder bore wear, have you priced a new cylinder for a 985 lately?
I wasn't seeing a problem, and I pulled several cylinders fixing oil leaks. The operator who had it before me had been using MoGas for years. Tulsa cylinders new for the 1340 weren't much different from a new Continental or Lycoming big bore HP cylinder when I was looking through TAP and paying attention. I never did need one though. I had a spare engine I never used either.
Tom-D
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I had a conversation the other evening with a guy who runs MMO in his fuel.
he must take a 709 ride with FSDO pilot pilot examiner, the Check ride pilot sniffed the tanks and refused to ride with him.
the check ride pilot said they were not allowed to ride in any aircraft that had auto fuel (STC) or any unauthorized additives in the system.
So now the guy is taking training in a rental ($1000) to be allowed to use the rental to take the examiner for the 709 ride.
dmccormack
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This guy must put a couple of gallons of MMO in each tank if the examiner could smell the MMO.....
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He may have taken one look and decided he didn't want to ride in the aircraft.
I wasn't there. Just relating the conversation. but I did see him disembarking a Regal aviation trainer. and knowing he wouldn't spend the money if he wasn't required to.
AEROBAT
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If I had a link I wouldn't know how to post it! I am not very computer savy but I will try to find an article for you. The Air Force used to by it by the drum for the the old radial engine planes like the Skyraider and T-28.
tonycondon
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in the glider club we had 3 or 4 beer kegs threaded with vented caps and a hand crank pump to fill it with auto gas that we bought at the ethanol-free station on the corner. worked very well
MBDiagMan
Final Approach
That's correct. The amount of energy available from the fuel is not determined by octane. Octane has to do with the RATE of burn.
Doc
Jay Honeck
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Marvel Mystery Oil is interesting stuff. I use it on squealing air conditioners down here in the salt air, and it's amazing. One shot of the stuff on the shaft, and no more squeak.
I've got one that was shrieking when we bought the hotel 16 months ago. One shot of MMO, and it's never made another peep.
I've got one that was shrieking when we bought the hotel 16 months ago. One shot of MMO, and it's never made another peep.
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If you had 2 petree dishes, one with diesel in it, and the other with 100LL in it and you ignited each which would burn faster?
yet which will detonate first in use?
It's all in the manner the fuel is used.