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  1. #1
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    Default How long does it take gas to go bad?

    I'm working on my own recipe for seafoam. So far what I've made smells the same...but that's the extent of my testing. I'm going to try it out in an old lawnmower engine to see how it cleans up the internals, but I want to test it's fuel stabilizing abilities. Aproximately how long does it take about a quart of gas to go bad?

  2. #2
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    Default Re: How long does it take gas to go bad?

    One year? If that's true why would anyone bother with fuel stabilizer over the winter? Also am I correct in thinking it goes bad faster in smaller amounts? I'm thinking now of using only about a pint of gas...just to speed up the testing.

  3. #3
    Supreme Mariner Boomyal's Avatar
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    Default Re: How long does it take gas to go bad?

    FWIIW, this summer I drew out about a pint of 87 octane gas into a clear jar for priming my carbuerator. I left it sit outside, with a cap screwed on, when I was done with it. After about a week, the gasoline turned cloudy. After about a month, the gas cleared up leaving a bit of curd settling out in the bottom of the jar. When it cleared it was a different hue than when it was freshly poured into the jar. I don't know what it means but it was a visual change in the gasoline. I ended up just pouring it back into the 5 gal lawnmower gas can.

  4. #4
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    Default Re: How long does it take gas to go bad?

    According to Chevron, it looks like about one year in a tightly sealed container in a moderate environment.There's some excellent information here: http://www.chevron.com/prodserv/fuel...term_gasoline/

  5. #5
    Supreme Mariner rickdb1boat's Avatar
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    Default Re: How long does it take gas to go bad?

    ZmOz Up until about 5 years ago, I never used anything when I stored my engine for the winter(5 Months). Never did have a problem with it in the spring. Never rebuilt the Carb or anything. Never used a decarb product. Still have the same little motor on my runabout going strong. It's an 89' Johnson 28 HP. So I have to wonder about all the additives we put in now days. But, like most, I do use Stabil and fog the motor every year before I put it up now. And I do decarb regularly, now. But, that's on my 91' 70 HP rude, not that it matters. Just a change in thinking or maybe reading these forums have changed the way I do things to preserve my motor. Then again, if I did nothing to it but run it every year and put it up in the fall until spring, like I used to, who knows....
    Rick

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  6. #6
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    Default Re: How long does it take gas to go bad?

    I'm with rickdb1boat on this one. There are 10s of 1000s of boats that are used each winter here in Florida and sit the rest of the year without stabil type additives. They start, run fine and don't wear out faster. Nothing happens to them. I've watched this happen for many years and it hasn't changed.

  7. #7
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    Default Re: How long does it take gas to go bad?

    Alway used a stabilizer in my boats. Never a problem.Forgot to put stabilizer in the lawn mower and a motorcycle. When I took them out of storage 6 months later, the carburetors had plugged jets on both. Cleaning the carb on the lawnmower was a piece of cake. Cleaning 4 carbs on the bike was a lot of work. Stabilizer seems like a real good investment.Six months and I was in trouble. Varnish in the jets, crap in the float bowels. Charles

  8. #8
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    Default Re: How long does it take gas to go bad?

    What's interesting is that my jug of STA-BIL says fuel deteriorates in 60 days, and that STA-BIL will last 12 months. Chevron says 12 months without stabilizer. Who knows?

  9. #9
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    Default Re: How long does it take gas to go bad?

    I agree with both extremes. I have observed more than once that if I leave an jerry can open for several weeks, the gas inside loses a lot of its volatility. Even hard to start a fire with it. I assume that the volatile component of the gas has slowly evaporated, leaving a higher concentration impure gas in the can (maybe the additives, or maybe gas breaksdown into more than one component - I don't know). I have also observed the drain lines in my outboard get clogged with a gummy substance if I leave any gas in the sagging portions of the lines after draining the carb bowls. On the other hand, I have left my tanks considerably full over the winter without stabilizer and drained it in the spring to use in lawn mowers and cars etc. There has never been a problem. It would appear to me that in large amounts, that is to say in containers that do not have a relatively large area to expose the gas to air, gas seems to last quite some time. The same is not true for smaller amounts.

  10. #10
    Fleet Admiral jtexas's Avatar
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    Default Re: How long does it take gas to go bad?

    I would assume that 2-stroke pre-mix would have different characteristics?Used outboard pre-mix in a lawn mower for two summers (same tank) before it gummed up so bad you couldn't turn the crankshaft. Trashed the mower & hired a yard man. That was 14 years ago & I haven't mowed a lawn since. "Sorry, hon, no lawn mower!"
    It's all about the tools.

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  11. #11
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    Default Re: How long does it take gas to go bad?

    I quit draining ob carbs for storage...in my experience all it did was speed up the sludging process and create carb problems. I learned this by mistake when I was out of the country for a year and didn't get a chance to run the carbs dry on 2 motors before I left. I came back and the the carbs were fine (before that I ran the carbs dry every time I used an outboard, now I never run a carb dry). For the next few years I left fuel in the carbs for 6-12 mos storage and still pulled the carbs down to check them. That was in 1974, I still have the same two kickers...which only get used once or twice a year to make sure they work. I don't use Stabil either, only because I haven't seen the need. This isn't saying Stabil doesn't work but I don't believe we have as big a problem as advertising leads us to believe. If it was that "critical" the FAA would dictate stabil type additive for airplane engines and the FAA makes mountains out of mole hills. Airplanes sit more than boats do and NOBODY uses stabil in their airplanes.

  12. #12
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    Default Re: How long does it take gas to go bad?

    Hmmm...interesting...guess I won't waste my time with a test to see how long the gas lasts. I've never used stabilizer over the winter either, but until this year the only thing I had that sat all winter was the lawnmower.

  13. #13
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    Default Re: How long does it take gas to go bad?

    Some of the problem with stale gas is associated with being left open to evaporate. Rememeber gasoline isn't a pure chemical like say toluene. It is a compound of many toluene, xylene, pentene, blah, blah, etc. Some of these are more volatile than others. Some of the heavy molecular weight stuff will polymerize (varnish) if some of the others go away (evaporate). Condensation in the air in the tank can cloud the gas and precipitate stuff. Some of the additives will oxidize in the air. Gas left in a full tank tightly sealed will last longer than gas left in a 1/4 full tank, and longer that a tank left with the top off.By the way piston engine airplane fuel is not gasoline, it is a different brew. It looks different and smells different. And every time they go to crank it up they manually check the tank for water.Anybody who makes something like Stabil is going to exaggerate the case for its use. They're not lying so much as perhaps overemphasizing the potential problem.One of the reasons I like oil injection on my Suzuki (which doesn't mix until the intake manifold) is when the gas evaporates it doesn't leave sticky oil crud everywhere which is half the problem with old premix.

  14. #14
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    Default Re: How long does it take gas to go bad?

    jimd,Airplanes have just as big storage problem as boat motors...probably worse. I don't know what the diffence is between aviation and car gas is other than higher octane and lots of lead. Either runs in cars or planes. Many experimental plane owners use car gas in their Cont & Lyc engines with lasting TBO results. And the grass roots drag racers come down to the airport to buy the higher octane fuel for street racing. The only problem I've heard is vapor lock in aircraft engines when using auto gas.

  15. #15
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    Default Re: How long does it take gas to go bad?

    Air craft engines during pre-flight have the floatbowl partially drained to get rid of crap. No the same as outboards. nevjb

  16. #16
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    Default Re: How long does it take gas to go bad?

    nevjb, all my boats are equipped with water separating filters that have a see-through bowl and water drain. "Pre-flight" for my boats include draining any crap...just like an aircraft.

  17. #17
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    Default Re: How long does it take gas to go bad?

    I've often wondered myself. I live in farm country and every farmer have bulk fuel tanks for both gasoline and diesel. Many fill it in the fall after the crop comes in and may not use it for 6-8 months but never seem to have any problems. I'm not aware of any that add fuel stabilizers so I assume either the fuel company is adding it or it is not neccessary for that storage term.

  18. #18
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    Default Re: How long does it take gas to go bad?

    HI! new gasoline today are made w some hygroscopic chemicals to prevent condens to build in tank... but this also makes the fuel brake down fast if not keept capped..specialy in high humidety.. tank vent and so on... alcohol is a big no-no...in the engine that is..he-he...

  19. #19
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    Default Re: How long does it take gas to go bad?

    My dad used to respond to such questions with another question.. "How long's a cats tail?"... Baffled me for years, now I understand. It depends on whose gasoline it is (what additives), how old it was when it was purchased, the temperarature, humidity, and what additives you may have added. All gasoline is not =, in the past few years there have been environmental laws passed which forced some additives to be reduced or removed from gasoline. Todays gas is not the same as it was a few years ago. I've seen many gummed up carbs from old gas, now use stabiler in all engines that sit and have not seen a clogged jet in over 3 years.

  20. #20
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    Default Re: How long does it take gas to go bad?

    What should you do if you think you have bad / old gas? Is there any additive that can help?Mac

  21. #21
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    Default Re: How long does it take gas to go bad?

    v12, i've seen some claims of such, but I don't believe it. Drain it and dispose of it properly and start with fresh.

  22. #22
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    Default Re: How long does it take gas to go bad?

    nevjb,Let's clarify the airplane storage deal. I'm a pilot and past plane(2)owner so will speak from my own experience. Planes sit for months or years between flights. Yes, fuel is purged in the preflight check and after fueling but it isn't the carb that is purged. The "delivery system" is purged. The carbs never get purged unless it is for problems or repair. I don't know what the gas difference is but you can take any auto down to the airstrip and pump 100LL av fuel into it and drive off. I used to see it every Friday evening with the street drag guys. It will run fine but I suppose eventually clog up the emission system. Otherwise you will just have a peppy engine that runs dirty. N276SP

  23. #23
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    Default Re: How long does it take gas to go bad?

    hello as a shop owner I will agree. yall please dont use stabil or anyother product. I really need the money that clogged carbs bring every spring. as far as aviation fuel it will make your outboard or most any other high performance motor actually run slower. I have extensive track and dyno sessions with a 68 camero with a 427 and several customers that race outboards. high octane does not mean its going to go faster and usually means it will go slower. most airplane engines dont turn anywhere near 5000 rpm. good luck and keep posting
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  24. #24
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    Default Re: How long does it take gas to go bad?

    I hope to pass the wisdom of the 1980s when the EAA or Experimental Aircraft got cargas approved for Airplanes. The answer they found is all car gas is not the same. Refiners start with a basic mix which has a natural octane and add airomatics to it to raise the octane. Airomatics boil off with temperature, lack of pressure, and leave the problems behind. Natural octaine gas like used in aviation do not have any problems with life and stay the same for years. Our car gas today is made from bases of lessor quality and is not held to a standard. Only the final mix with the aeromatics added is tested for octane. The reason they are called aeromatics is this octance boosting substance is the smell of car gas and raises the base to the octane required for sale for car use. Aeromatics also are responsible for swelling rubber gaskets and other parts that would affect airplanes. As the abiliity of octanes boosters have gotten better at boosting of poorer bases they have not necessarly been good as enhancing the life of poor quality bases. For people who want the answer, use 100LL avation fuel or even 80 octane no lead if available. 100 Low lead contains 2.5 ML per gal lead which is what all early marine engines were designed for.

  25. #25
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    Default Re: How long does it take gas to go bad?


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