Lycoming write up on use of mogas...interesting

[cjensen]

See the article starting on page 17.

There is a TON of good info here for anyone running a Lycoming or clone.

Lycoming Key Reprints-Use of Auto gas

[Larry D]

Chad,

Please read the other posts on mogas in this forum. I suggest you go to the EAA website and read their information on auto gas in aircraft engines.

You might notice that other engine manufacturers such as Superior and ECI are selling engines (clones) they say can be run on mogas. Rotax aviation engines use auto gas.

The Lycoming article has some useful information but you must realise there is some CYA there.

All gasolines including aviation gas can form gummy deposits on long standing. It is not a good practice to leave auto or aviation gas standing in the tanks of your plane for long periods. Especially in conditions that promote evaporation of the most volatile components. Full tanks are better than partially filled because that limits air and moisture invasion. Oxygen reacts very slowly with the unsaturated hydrocarbons in gasoline causing some crosslinking.

As long as you are aware of the limitations of the engine it is not necessarily unsafe to use auto gas. I have an RV-9A with a high compression engine (9.2:1). I only use 100LL avgas in that engine. High compression engines need the higher octane to supress detonation. I have a low compression 1975 Cherokee that is run mostly on auto gas. The Cherokee which has an STC for auto gas has run very well in hot and cold weather, had no fouled plugs or other problems, has accumulated 2000+ hours and is doing well. Guess which plane has had two instances of detectable fuel vapor problems. Not the auto gas Cherokee! Due to EPA requirements the vapor pressure of auto gas has been lowered in many parts of the country. So the vapor pressure isn't as likely to be a problem as it might have been 20 years ago. All indications are you should not run gasoline with alcohol at this time as some fuel system components may not be compatible with the alcohol and alcohol is a co-solvent for water in gasoline. That means it stabilizes the dispersal of water in gasoline. However this stabilization is temperature dependent and decreases with lower temperatures. In cold temperatures excess water could separate.

I have followed the avgas/auto gas arguments for many years. It appears that in the not too distant future we may all be using auto gas. Are you aware that there is currently a suit to extend the ban on lead in gasoline to avgas? Economics and political pressure from enviromentalists will eventually win.
The point you bring up in the Lycoming article is they tell you not to use auto gas. Think about this. If an engine fails then it is not unlikely the engine maker will be sued. If the engine maker can say "you used auto gas and we told you not to" then they have a convenient argument to defend themselves even though the fuel may not have been the cause.

I have gone on long enough.

Larry Dickinson (chemist)
RV-9A 135 hours ( on avgas)
Atlanta, GA

[cjensen]

Larry,

I appreciate your response. However, there is no need to direct it at me specifically. You indicate at the end of your post "The point you bring up in the Lycoming article." I didn't bring up any point, Lycoming did. I didn't write it, and I'm not proclaiming this as gospel. In fact, if I put an Eggenfellner Subaru in my 7, I WILL use auto fuel (while testing for vapor pressures, clean fuel, etc...), but that is a different subject. I'M not saying not to use Mogas. I just found the write up interesting, and I hoped others would as well.

I know you don't know me or my background (as I don't know you, other than you're a chemist), but I can assure you that I have followed all threads on Mogas here, EAA articles, AOPA articles, among others. I work at an FBO and fly as a professional pilot. It does pay to know of this subject working in the aviation industry.

I'm not saying I know everything there is to know (who does?). My post was simply a passing of information from Lycoming. We get the Lycoming Key Reprints at work, and the link takes you to the latest version (2006) which they print every four years.

I am aware of the suit on the ban of lead, and I agree with your statement that enviromentalists will prevail somewhere down the road.

Please take some time and read the rest of the reprints. They are great info...

I'm mean absolutley no disrespect with this response.

[Barry]

Here is a link to work done by a company in Switzerland who provide STCs for the use of Mogas in Lycoming airplane engines.

http://autofuelstc.softworkx.ch/index.php?id=4&L=1

On the rare occasions when I have had to use Mogas in my Lycoming O360 I have never noticed the slighted difference in the way the engine runs. The CHTs and EGTs on all the cylinders were the same as with 100LL. I once owned a Continental O200 Jodel and that was always run on Mogas with no apparent problems.

I tend to believe there are two type of people. Those that have never used Mogas in their airplanes and say it does not work and the other type of person who uses Mogas and never says anything about it.

Barry

[Steve]

I agree with Barry about the quiet people. I know a guy who had a Tri-Pacer. He didn't want to pony up the $135 (1 buck per hp) for a certificate/placard/label allowing him to legally run mogas in the plane. When using 100LL, the plugs would foul before reaching the runup area but would run great on 88 octane midgrade mogas.

Steve Fabiszak

[jonbakerok]

I never use mogas in my RV, but I sure wish I didn't have to use 100LL. I could care less about the environmental stuff, I just don't like paying a ridiculous premium for an additive that is actually detrimental to my engine. Well over 90% of the fleet doesn't need 100 octane leaded gas. Hasn't anyone else noticed how much better our cars work since they got rid of leaded car gas?

We should beat the environmentalists to the punch and lobby for unleaded 93 octane AVGAS.

I used to have a 150hp Cherokee. Running straight 100LL in it was positively dangerous. I had to pull the plugs every 25 hours and dig out the lead chunks, just to keep it running. But the alternative of running mogas wasn't much better. Carting around car gas twenty gallons at a time in the back of my SUV in the winter was an act of lunacy. Simply entering your vehicle in the winter generates about enough static electricity to power Al Gore's mansion for an hour or so. It's a miracle that airports aren't pock-mocked by the blast craters of unlucky mogas users.

Mogas is nasty stuff. When I'd sump the tanks in the Cherokee, it looked like one of those glass balls you shake to see it snow on the Empire State building -- only the snow was that brown goo that precipitates out of mogas anytime it sits unused for more than a couple of weeks. Not to mention it stinks and makes ugly brown stains on your plane that can't be removed instead of pretty blue stains that wipe right off.

But here's the thing. If we let the environmentalists force the end of 100LL, that'll be it. They'll just end it and we'll all have to figure out how to make mogas work. But if we take the inititive, we might be able to talk them into giving us an alternative AVGAS that has a low vapor pressure safe for high altitude use, that's stable for long periods, that has consistent quality with no alcohol -- and maybe even doesn't stink.

Oh, and here's another thing to consider. They're getting ready to stick us with a 70 cent tax on avgas. That's enough to kill GA, but it's a fraction of the road use tax we already pay on car gas. If avgas wasn't so expensive in the first place, we'd never notice the tax. Think about it. When you put mogas in your plane, you're paying a road-use tax that's higher than the 70 cent air-use tax the FAA is proposing -- and it's still a dollar cheaper than 100LL AVGAS.

[n2prise]

Since there is lead in AVGAS, it cannot go through the pipelines with unleaded. It is trucked or put on barges wherever it goes. That is one reason AVGAS is more expensive than auto fuel.

Jerry K. Thorne
RV-9A N2PZ
160 HP ECI O-320, 100LL
213 hours TT

[Larry D]

I believe it is in everyones best interest to read the available information and then make an informed decision whether to use mogas.

If you conclude that the quality or other characteristics of the mogas available to you is unsuitable for your use then don't use it. The money saved would be inadequate if a failure resulted from the cheaper fuel.

Lycoming has printed the same blanket statement about auto gas in its bulletins for many years. Notice that it refers to additives to clean carburetors. I don't know of any auto built in the last twenty or more years that has had a carburetor.

I believe it makes good business sense for Lycoming to make that statement. Many of their engines would not perform safely on low octane auto gas. Most pilots probably don't know about the different methods of determining octane. They are different for aviation gas and auto gas. Auto gas octane numbers are higher than they would be if tested by the method used for avgas.

To use auto gas the engine should be tested for its use in the aircraft. In an experimental airplane that means you the builder/manufacturer are responsible to determine that the fuel is adequate to the task. To obtain the STC for auto gas use each model of a certified airplane had to be tested and demonstrate that there were no problems associated with its use. My Cherokee has been tested. My experience with the Cherokee is that the engine performs the same with auto gas and avgas. The auto gas has eliminated the lead fouling problems encountered prior to use of auto gas. So less maintenance and lower cost make the use of auto fuel a success for me. I transport the auto gas a short distance in five gallon approved containers in my pickup truck. I would not transport a large quantity of gasoline inside an SUV or auto. There is inconvenience to fueling with gas cans especially with a high wing airplane. The Cherokee is low wing of course as are the RVs. In any case, the pilot should always determine that the fuel is of adequate octane, free of alcohol, clean, and free of visible of water.

Again, if you think you might someday want to use auto gas read the available information from many sources. Then you can make an informed decision.

Larry Dickinson

[airguy]

I keep seeing references to carrying fuel in 5-gal cans in vehicles - maybe it's just my rural upbringing (thank God for that!) but the answer is crystal clear to me - though I understand that this is certainly not possible for everyone. I will have a 50-gallon tank with 12-volt pump in the bed of my pickup, just like you see for diesel service on any self-respecting farm anywhere in the US, but filled with 92UL. Add a 10 foot hose with pump handle, and a static line for grounding, and you've got a genuine fuel truck.

[frankh]

Worked great until he left his truck outside in Oregon one too many times. His enging quit taxiing to the runway.

He then drained 2 gallons of water out of his tanks!

He was a lucky boy!..

Frank