Stale Autogas

[JumpNurse]

I assure you auto gas can and does go bad. I've seen it many times in my previous life as an auto mechanic. Usually it is on the order of many months to years before it happens, but it does happen. When it does, it is a real pain in the rear. I'm not sure of all of the chemical changes that occur, but it starts reeking havoc on rubber parts like lines, o-rings, gaskets, fuel pump diaphragms, etc... Storage time seems to vary on whether you are using summer fuel mixes or winter and the part of country you buy the fuel in. I don't know what Rotax would say but I would not hesitate a second to use Stabil if I wasn't going to fly it for over a month.

[DanWright]

I have had to clean multiple carburetors gummed up by autogas sitting in them, mostly motorcycles. I have a a 1000cc Kawi waiting for just such attention in the garage now.

[N223JH]

OK, Stabile it is. Glad to see nobody found it verboten in the unter-print portion of the Rotax warranty. Stuff works great in my chainsaw and old cars.

Jim

[bruceh]

I have had experience with old gas clogging the carb on one of our ATV's. We only run these in the winter months when it is "desert season". The rest of the year they sit in an enclosed trailer. Our first outing after about 6 months of storage had one of them that would idle fine, but would stumble and quit when you hit the throttle. Opened up the float bowl on the bottom of the carb and found some sticky green goo plugging up the main jet. Hit it with some carb cleaner and back to working just fine. I've only had the 1 problem and this is over 7 years of use/storage of 5 ATV's and 1 motorcycle.

[videobobk]

Maybe really off topic, but I can say how LONG 100LL lasts. A few months ago a Cherokee that had set out for about two years, and had been in a hangar before for a long time, was rebuild and flew on the original 100LL. It was last refueled in 1997 and did not cause a problem! I wouldn't have done it...

Bob

[380mxc]

google phase separation for the life of auto gas

[allbee]

my thoughts on how long fuel should stay in your aircraft. No more than 2 months. If it were mine i would drain it out and put it in my truck, than refill. Of course the real cure is to FLY MORE

[twsurveyor]

Originally Posted by N223JH

While fueling my 12 yesterday, was approached by an RV10 builder who informed me that, "Car gas goes stale in two weeks and will eventually gum up those carburetors."

Jim, Given the fact that our "auto gas" is produced from crude oil that comes out of geologic formations that are millions of years old, I find it hard to believe that 2 weeks will make any difference at all? Think about it!!!!

[N1593Y]

Originally Posted by 380mxc

google phase separation for the life of auto gas

Phase separation only applies to ethanol blended gasoline. I hope everyone understands that if you put gasoline in your airplane and water gets in your tank, you can drain the sumps to get it out. If you put E10 in your tanks, you should NEVER see water when sumping the tanks. If you do, your E10 has phase separated and what you have in your tanks is a very corrosive water ethanol mixture at the bottom that you just sumped, and an unidentifiable fuel, the specifications of which you have no idea. Your entire fuel system should be drained and inspected. Phase separation is irreversible, you cannot just add more E10 or gas.

Gasoline aging is discussed in many places. Ben Visser just did an article about it at the GAN web site and his opinion is auto fuel should have no problem sitting for six months, and 100LL for one year.

My opinion is that if you buy auto gas from a major brand, i.e. Chevron, Shell, Texaco, Conoco-Phillips, BP, Tesoro, etc. it will last a long time. Modern mogas is made to very tight specs because of all of the EPA rules and if it was as bad as some claim, your fuel injection system and pollution control systems would be toast in no time. This is not to say that the best gas cannot be turned into some unrecognizable chemical during transportation and storage. Your opinion may vary.

E10 is entirely another matter. My opinion is that it has no place in aviation. Why would you put something that has less energy, attracts water which may cause phase separation and is more corrosive in an airplane you built. I wouldn't.