I have the Peterson STC for MOGAS for my 235 (O540 B4B5), I am running out of places to get Fuel without any Methenol blended with it. Been reading about the negative effects Cars have running the 10% blend, such as reduced MPG, higher temps, water in gas, and the breakdown of the Rubber fuel lines, and gaskets located in the fuel pumps, carbs, etc. What about running this blend in our Aircraft, anybody heard or any negative effects yet?
BIG negative effects, like the one that allows Your insurance company to deny a claim if You have an accident with it in Your fuel lines when You crash. Since the STC doesn't allow alky in your mogas that constitutes a violation and renders Your aircraft "un-airworthy". Bob, I have the same plane and although the pumps here in SoCal have stickers that warn "up to 10%" may be blended, I haven't seen any fuel with such (Yet). I buy my Mogas at a local shell station and check it for alky every time. Last week when I filled my re-fuel trailer there was no detectable alky in that batch. I went around to the local stations doing tests a few months before I decided to build the trailer and start using Mogas and settled on that station because it had the lowest consistant level. I do keep pure 100LL in the tip tanks for take off (see the "Mogas STC" af a couple weeks ago in general discussion) and can tell You the fiberglass tip tanks won't hold Mogas very long. I have used Mogas with 3% alky and haven't suffered any fuel system rubber component deterioration but the fuel hoses have all been replaced with teflon lined hose and I switch to the tips (100LL) right after I land, so avgas is in contact with nearly all components of the fuel system while the plane isn't being flown.
Mogas doesn't normally ever have any methanol in it unless you add some in as a fuel system dryer ("Heet" gas line dryer comes to mind), or buy methanol racing fuel. Ethanol (Everclear, good old Ozark mountain moonshine) is the type of alcohol they use to contaminate mogas these days. A terrible waste of perfectly good corn squeezins if you ask me.
Methanol will corrode aluminum fuel system components rapidly. Ethanol corrodes aluminum less rapidly. Both will play havoc with any fiberglass tanks, and also deteriorate any rubber components in the fuel system, or the polysulfide (Pro Seal) gas tank sealant.
Based on my tests with ethanol blended gasoline, up to 10% blended has no measurable effects on fuel bladders, polysulfide sealants, gaskets, carb floats, fuel sender floats, or steel or aluminum fittings found in typical aircraft fuel systems.
Straight ethanol does all the bad things you hear about. But 90-95 percent mogas with ethanol blend does not. The solution is just too weak. Corrosion only appears where excess water is allowed to be in contact with reactive materials. It's not the ethanol, just that the ethanol makes water more likely to condense from the air in the tank on a humid day.
Nor does vapor lock appear until the blend goes above 25% on a very hot day- 90 degree and up seems to be the trigger point with engines exhibiting fuel boiling and associated flooding when trying to re-start quickly after a shut down. (as you would when re-fueling) But then crank the engines for 30 seconds with the boost pumps on and the problem goes away.
I would suggest that the mogas STC people do a few tests to allow blended fuels to be used under appropriate conditions. It's certainly possible and we need to address asap.
That is very good advice on switching to 100LL after landing to have it in the fuel lines when the AC is not in use. I have never used the 10% methenol blend in my tips and i do not leave any fuel in them at all. I burn evry single drop out of them then purge the 1 or 2 ozs that the fuel line can't pickup by opening the drain and then take off the fuel cap while i am putting the AC away. that gives the tanks a chance to air out and dry out.
Here in Florida 85% of the gas stations have the little sticker on the pumps that says "Contains no more than 10% Methenol".
I am starting to use a 33% 100LL to 66% Mogas blend in the main tanks and like i have always done a 100% 100LL in the tips.
I would imagine that someone is working on a modification/parts upgrade to use Methenol.
It is not methanol. It is ethanol. If I am not mistaken, methanol is wood alcohol and ethanol is from the corn. Ethanol is what they are adding to gasoline.
So you guys have been burning ethanol blended gas in your planes? I wish I could get some real data on it, but the FAA sure does not approve of it.
I have inadvertently put a tankful of 10% ethanol mogas in my plane before. I thought it was ethanol-free but later found out it wasn't. I also let it sit in the tanks for almost three weeks and here's the negative things I discovered: It left a gelatinous filmy membrane-like residue forming in the bottom of the tanks that drained out in pieces when I sumped the tanks. Also it made tiny bits and pieces of the black tank sealant which lines all the riveted seams in the tanks start coming loose. The airplane ran fine on the gasahol the hour I flew it, and after I discovered it contained alcohol by doing the water test after being suspicious of the filmy residue, I drained most of it out into jerry cans as I could for use in my lawn tractor instead, and refilled the tanks with straight 100LL. Both the filmy residue and the black specks from the sealant stopped happening after running two tankfuls of avgas thru the plane. I only buy premium unleaded mogas now, and always do the water test first, and using known-good mogas I have no issues at all.
As I mentioned, The pumps here in SoCal have stickers that say the gas may contain up to 10% but I haven't seen gas with anywhere near that amount yet. (I test every time) Have some of You others that use Mogas been seeing fuel with 10% in it? (If so, where are You located?)
Bob, I also mix a little 100LL in with the mogas but only about 9% (10 gallons of 100LL to 100 gallons Mogas) With the pure 100LL that gets run during taxi, take-off, & the initial climb, the engine gets all the lead it could ever need. Probably way more than enough. I also have the Hodges tester Petersen sells and check my Mogas blend on real hot days but have yet to see it warn me of potential problem. I have seen the fuel pressure at zero on the ground once or twice after a quick re-start in hot weather though. (The engine didn't quit but I was only taxiing so fuel flow requirement was low)
