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Discussion in 'Maintenance Bay' started by Tom-D, Aug 10, 2018.
How old is too old? what would be the oldest fuel you'd feel safe flying with?
The article states one year for 100ll and six months for mogas. Seems like a reasonable yardstick, but probably quite conservative. I have used regular pump gas in a car up to three years old without a problem. Although I wouldn't try that in my plane.
1 year, 2 months, 22 days, 46 minutes and 22 seconds and not a moment more.
Do you need to account for leap years or is that extra day a freebie those years?
100LL is loaded with stabiliziers to begin with. I'd not be overly concerned. Mogas is more problematic.
Leap year gives you an extra day for free unless it is held in tip tanks, but then all bets are off.
I would at least drain some and get some new fresh avgas.
Marvel Mystery Oil, thats the answer, or Seafoam.....
....and enjoy your smoke trails.
If MMO is the answer, you have asked the wrong question.
My ride sat for about 5-6 months last winter with a mix of 100LL and auto fuel in one tank. Ran just fine on it.
I would not put anything other than avgas in my wet tanks, never know what effect MMO/ethanol/STP could have on my 40 year old sealant.
SOP for my oil changes is to pour some MMO into the oil, go flying for an hour, then change the oil. Maybe it’s wishful thinking, but I swear the engine sounds better.
You guys just dont appreciate the miracle that is Marvel Mystery Oil. I hear it cures bursitis too!
Well,,,, the 182 I'm working on has sat for 10 years (maybe more) don't know when the fuel was put in.
Doesn't give me a warm and fuzzy using the old fuel.
So, I was wondering how old the fuel can be, and still be usable.
It isn't your aircraft, therefore not your concern. Do the work you were contracted to do, raise your concern to the owner and let him decide what he wants to do. If he is happy with old gas, that is his decision and he can own any consequences from it.
If the fuel is confirmed to have sat in the tanks for 10 years or more, than I’d definitely drain it and purge the whole system. It isn’t good fuel.
Don't know if it's an OWT or not, but I've heard stories of barrels full of fuel being found on Pacific Islands that were left over from WW II. And it burned just fine.
I guess anything is possible. I’ve had gas go bad just sitting in the lawn mower between seasons before. If it were me, I wouldn’t want to fly with 10+ year old stagnant fuel.
A sealed barrel vs. a Cessna vented fuel tank + condensation. When we drained ours we used the old gasoline for cleaning stuff. Twenty years ago that was OK, apparently not today.
Modern fuel with ethanol I would not leave in my tanks for 6 months, straight gas,diesel no problem, but 10 years?
I wonder how many lawn mowers use 100LL. ?
These tanks are completely full, the fuel I've drained looks just like 100LL should.
Plenty, but I doubt they will run on 10 year old 100LL!
I was hoping that some one could tell why that is?
Big romping stomping chest beating chemists on this page, would call you out for mis-spelling (Zink), and will argue all day about refinery operations, Yet not a peep out of them when asked about 100LL.
I really don't believe that.
Common way of disposing of old gas.
Point is, no matter what type of fuel it is, I wouldn’t want to fly with fuel that’s been sitting stagnant in my fuel tanks since 2008 or prior to. If you’re willing to take the chance, than by all means, fly it.
Tom isnt really asking us our opinion. The quote below gets to the crux of the matter. Tom is itching for a battle of wits with someone. This has nothing to do with actually flying with old gas.
Huge difference 'twixt the stability of aviation fuel and auto gas.
I'm not saying that I'd fly with 10 year old aviation fuel either. Just saying you can't compare the two.
Wish Clark was still around to chime in.
She ain't what she use to be.
All 4 of mine do. It doesn't go bad like unleaded with ethanol.
I've seen 10 plus year old 100ll used, no problems. Go figure.
I wouldn't, but to each his own.
Would you leave my ex-wife out of this please!
I guess that's why they sell gas stabilizer.
I have no clue about the answer to Tom's question, however.
The general recommendation is apparently 12 months but to be honest that number has likely been drawn out of a hat and conservatively established.
Chemically, what happens to petroleum based fuels like gasoline over time is peroxidation and polymerization. The former will reduce octane (peroxides are apparently more prone to knocking) and the latter will contribute to gum formation. Peroxides may eventually be converted to acidic compounds. When these effects will become of practical significance is hard to establish, as it depends on the chemical composition of the fuel (a gas is a complex mixture of substances, which include alkylates, aromatic compounds, and olefins, e.g.), availability of oxygen, humidity, temperature, and time. I would suspect it would take a long time to reduce the octane from 100 to something you couldn't burn in a low compression engine, but I would be more concerned about gum and acid formation in the fuel over a long period of time exposed to air. There will also be significant evaporation effects over a 10 year period which concentrates peroxides and any gumming agents, and may alter the composition of the fuel. Again, the exact effects and their practical magnitude are difficult to assess with certainty. My chemistry sense would be more worried about potential gumming than octane degradation, but that is not very objective.
The only way to know for sure is to send out a sample of the fuel for testing, but that may or may not be cost effective compared to replacing fuel. After that length of time I would definitely want the fuel system and carb (if applicable) to be thoroughly cleaned and degummed. And if it were my plane I would just replace the fuel. That way you know what you have with zero added risk.
In Engineering we call that a "rectorandom estimate" and it isn't drawn out of a hat, but another spot on the anatomy.
Glad you see my point.
Jabiru say mogas with alcohol stratifies and can affect the wing sealant.
In chemistry and economics it's called the SWAG method, which is a slight improvement on the WAG method.
Tom- Comments like this really don't make you popular here.
The question was answered in the first reply, in the link provided. I felt no need to repeat what was already well stated. The more volatile components evaporate out, there's polymerization of some of the alkene components, as stated elsewhere in the thread.
Since you chose to bring it up, aside from not knowing how to spell "zinc", call outs were for these as well:
Calls ammonia an acid: https://www.pilotsofamerica.com/community/threads/paint-stripping.101772/#post-2244913, doubled down here: https://www.pilotsofamerica.com/community/threads/grumman-aa-5b-mechanic.106644/page-3#post-2400188
Claims water isn't a solvent here: https://www.pilotsofamerica.com/community/threads/corrosion-treatment.102604/
Came up with his own term of "jellied acetone" and claimed it was a paint stripper: https://www.pilotsofamerica.com/community/threads/chemical-strippers.101866/#post-2249982