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Stale Autogas

N

N223JH

Well Known Member
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."

While I believe he is mistaken in the period of time required for the gas to go bad, it prompted me to query the group on collective knowledge. My experience with gasoline engines tells me that it takes more on the order of several months for varnish to appear in the carb's smaller passageways.

I'm flying 1x-3x a week now but I wonder if draining the tank and "running it dry" wouldn't be a bad idea for extended down-times.

Additionally, I do not recall if there was a specific prohibition regarding fuel stabilizer use in the Rotax paperwork (not at the hangar right now). Sta-Bile works well in chainsaw, lawnmower, etc-.

Thought maybe some of y'all might have some practical experience and/or authoritative reference bearing on these subjects.

Jim
RV12 #120264
flying 15 hours
 
I have 300 gals of premium at a time delivered to my overhead tank ay my farm hangar and I treat the entire 300 gals with Stabil . I have had no problems doing it this way for years. I believe folks at Lockwood (Rotax center) recommended Stabil.


Brad stiefvater
Salem SD
 
I have the 912uls and I have gone a week without flying it. I use E10 all the time. If it goes a little longer I put in the pink stabil and still no problems. Sounds like you have nothing to worry about. I only fill my tank half way so I can put in fresh on a constant basis. hope this helps. Oh and make sure you buy your gas at a station that sells a bunch of fuel, that way you know it's fresh.
 
What I have done - -

Cold weather may slow down negative affects, but I have let a 912ULS sit for 2 months of cold weather, and didn't seem to make any difference. I think there would be many factors to consider. I wouldn't worry about it. Add some fresh if possible, and fly.

John Bender
 
Phil Lockwood at the IL Ultralight Safety Seminar last year, recommended Sta-Bil if the fuel sits in the plane's tank or storage tank longer than 1 month.
 
If there were a risk of car gas going stale because every last drop isn't used up, there'd be at least a couple of dead cars out there...
 
Another story - only of interest - -

I bought a 1 year old 'builder' car 5 - 6 years ago. Decided not to finish it then. Left it sit for 4 1/2 years ( inside), then decided to finish it. Put a battery in it, and it started instantly, and run like it had been fueled the day before. I know cars can compensate for many ills, but as I said, an interesting story.

John Bender
 
bad gas

I've heard this "gas goes stale" stuff for years but I've never seen it.

I've had yard equipment with 2-4 yr old gas in it that ran fine - never a problem.

How do these rumors get started?

Dave
-9A flying (out of ph 1 testing)
 
I think the problem is not so much the fuel goes stale, but when a significant portion can evaporate, the stuff remaining looks and smells like varnish. This is particularly a problem on carbureted engines. Fuel evaporates from the carb, and the float valve opens, replenishing the evaporated gas. Eventually the goo in there becomes essentially "condensed" gas. For carb'd engines that are stored, some sort of a fuel shut off valve is important to prevent this. Additionally, the fuel may be undergoing some sort of chemical reaction in the presence of air, I don't know.

If I had to guess, I'd think Sta-Bil might work simply by forming a skin on the gas? It smells a lot like diesel fuel...
 
I had gas go bad after 6 months or so in the lawn mower. it barely ran and produced a lot of white smoke. I believe it was an eth/ gas blend, and the last time i ran eth in any of my small engines
 
Yep

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.
 
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.
 
Thanks for the input...

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
 
another data point

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.
 
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
 
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:D
 
Stale Autogas????

N223JH said:
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."
Click to expand...

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!!!!
 
380mxc said:
google phase separation for the life of auto gas
Click to expand...

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.
 
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