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Thread: Does gas really go bad?

  1. #1
    Vulture of The Western World Eric's Avatar
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    Does gas really go bad?

    Does gasoline really go "bad" if you leave it unused for a period of time? Some people are convinced this is just another urban legend - and that people who worry about "old gas" (and spend money on fuel stabilizer) are wasting psychic energy as well as money.

    But in fact, gasoline can degrade over time - and that can lead to a number of problems, ranging from hard starting to rough running to no starting at all.

    Here's why:

    Unlike crude oil, gasoline is a highly refined product brewed to a certain chemical composition with very specific characteristics, including, for example, volatility - a term used to describe how easily (and under what conditions) the gas vaporizes so it can be efficiently burned in your car's engine. But the most highly volatile components in gasoline also tend to evaporate over time. As they do, the remaining fuel's volatility - and ability to combust properly - degrades. The less volatile the fuel, the less effectively it burns in your engine. The result is diminished engine performance. Your engine may still start and run. But it probably won't run as well. The good news is the problem should cure itself - once the old gas has been consumed and the tank's topped off with fresh fuel. Evaporation of volatile compounds can be limited by making sure to top off the tank and by checking to be sure the gas cap is secured tightly. (For the same reason, be sure all portable fuel containers are sealed tightly as well.)

    The next problem is oxidation - and it's more serious.

    Hydrocarbons in the gas react with oxygen to produce new compounds that eventually change the chemical composition of the fuel, leading to gum and varnish deposits in the fuel system. These deposits and impurities can clog up fuel lines and filters, as well the small orifices in a carburetor (jets) and the even smaller orifices in a fuel injector. Removing these deposits can be expensive - and your vehicle may not run at all (or run very poorly) until they are removed.

    Lastly, there's water contamination. Condensation from heat cycling can form inside your gas tank and lines. (Water contamination is also a problem at gas stations with light traffic, for the same reason. The underground storage tanks experience increases and decreases in temperature - and this can cause moisture to form and contaminate the fuel. When you fill up at such a station, you're pumping in the water along with the gas. Such low-traffic stations may also have other contaminants in their underground storage tanks, such as rust. They are best avoided when possible)

    Fuels such as E85, which have a high concentration of ethanol alcohol, may be even more susceptible to water contamination as ethanol likes to draws moisture out of the surrounding air.

    Water, of course, does not work too well as a fuel in an internal combustion engine.
    It will cause hard starting and rough running until it's purged from the system. It can also contribute to internal rusting of the fuel lines and tank. The resultant scale and small particles can create a true nightmare - sometimes requiring the replacement of the lines and tank at considerable expense.

    You can reduce the chances of water contamination by keeping your car's gas tank as close to full as possible - especially if the vehicle is going to be left idle for an extended period.

    How to identify bad gas?

    One way is to eyeball it. Oxidized fuel often turns darker over time - and may even smell sour. You can check stored fuel by pouring some into a clear glass container and comparing it side-by-side with known fresh fuel. If your old sample looks noticeably darker than the fresh fuel you have strong evidence the fuel's gone bad.

    How long does it take for gas to go bad?

    That depends on a number of factors. For one, it's hard to know how old the gas you just bought actually is. It may be fresh from the refinery - or it may be a month old already by the time you top off your tank. Some fuels also are mixed with better (or more) oxidation inhibitors than others. But it's a good rule of thumb to avoid leaving gas in your tank (or a storage container) for more than a coupe of months, if you can avoid it.

    And if you can't?

    Then it's a wise move to buy some fuel system stabilizer and mix it in with the gas before you put the vehicle into long-term storage (or leaving your lawn equipment fuel containers sitting for the winter). The stabilizer helps prevent oxidation - the "biggie" that can turn gas into a garbage that gunks up your system and which can lead to expensive repair work.

    Using fuel system stabilizer for extended storage is preferable to draining the tank and leaving the system dry - which can cause rubber hoses, gaskets and seals to dry-rot and crack (possibly leading to leaks and even a fire), in addition to exposing the insides of metal fuel lines and your gas tank to air and moisture - which can lead to (or accelerate) the formation of rust.

    Fuel system stabilizer is not a cure-all, however - and it doesn't last forever. It must be mixed with fresh gas before the vehicle is stored - not added to already old gas. And while it can slow down the oxidation process and keep gas fresh for as long as 12-15 months, if you're going to leave the vehicle parked for longer than that, you may want to drain the tank and refill with fresh fuel before returning the vehicle to service.

    END


  2. #2
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    Re: Does gas really go bad?

    I've got a couple of 5-gallon cans of gas in the garage (the nearby station tends to run out during high-traffic weekends, and I have a 64 mile round-trip commute). I put some stabilizer in it about 6 months ago. I think I'll put it in the car this week and buy some fresh to replace it.

    Chip H.

    Former owner: 2012 Honda Civic LX, 2006 Honda Ridgeline RTL, 2000 Honda CR-V EX, 2003 MINI Cooper S, 1992 Honda Accord LX, 1999 Mercedes ML-320, 1995 VW Jetta GLX, 1991 Mercury Capri XR2, 1981 Mercury Zephyr, 1975 Chevrolet Impala

  3. #3
    Vulture of The Western World Eric's Avatar
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    Re: Does gas really go bad?

    Quote Originally Posted by chiph
    I've got a couple of 5-gallon cans of gas in the garage (the nearby station tends to run out during high-traffic weekends, and I have a 64 mile round-trip commute). I put some stabilizer in it about 6 months ago. I think I'll put it in the car this week and buy some fresh to replace it.

    Chip H.
    I try to avoid any problems with old fuel by starting and running all my vehicles - cars down to weed whackers - often enough that the fuel in them is never more than a couple months' old. And I always use Sta-Bil for any fuel that will be left unused for more than a month or so...

    So far, so good!

  4. #4
    DonTom
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    Re: Does gas really go bad?

    "and keep gas fresh for as long as 12-15 months,"

    But will it keep the gasoline good for 15 months LONGER?

    Since I have held gasoline in tanks for more than 15 months countless times (without any fuel stabilizer) with no problem, I am not convinced of any advantage to the fuel stabilizer.

    And not just here in the SF area. Also, in NV, where I only ride my motorcycles for a day or two in summer. Also, my RV. There the winter weather sometimes gets below zero and summer gets above 100F.

    BTW, I do have some unopened bottles of fuel stabilizer. When I read it "keeps fresh gasoline good for up to one year" I decided not to use it. Why change from what works? And if gasoline had fuel stabilizer in it when fresh, in three years would you be better off with or without the fuel stabilizer?

    BTW, this summer, I do want to get a chance to ride my two motorcycles and RV left in NV enough miles to go through a full tank of gasoline in each. I need to go through 50 gallons in the RV -- regardless of gasoline price!

    The BMW left here in SSF, Kalifornia is even over my limit on how long I would want to keep gasoline in it (at least three years, but I think four). But I am temped to try it as is and see what happens. What is the worse that can happen, just gummed up carbs? It's easy to take apart.

    Skeptic Don



  5. #5
    Senior Member Kwozzie1's Avatar
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    Re: Does gas really go bad?

    But will it keep the gasoline good for 15 months LONGER?

    Wow!
    I couldn't go for that long without drivng any vehicle ;D
    Rex
    On the Sunshine Coast, in the Sunshine State Queensland (QLD), Australia

  6. #6
    DonTom
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    Re: Does gas really go bad?

    "And I always use Sta-Bil for any fuel that will be left unused for more than a month or so...

    So far, so good! "


    And I have NEVER used it, not even in things that would not be used for YEARS.

    And so far, so good!

    And I am considering starting and running my BWM with it's four year old gasoline just to see what happens!

    -Don-

  7. #7
    DonTom
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    Re: Does gas really go bad?

    "Wow!
    I couldn't go for that long without drivng any vehicle Grin"


    But counting my boats and motorcycles, I own a dozen or so vehiclles. Makes it rather easy to ignore a couple of them for years.

    -Don-

  8. #8
    mrblanche
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    Re: Does gas really go bad?

    I would be more afraid of tires that were that old than gasoline.

  9. #9
    Vulture of The Western World Eric's Avatar
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    Re: Does gas really go bad?

    I'd say you've been fortunate - and are pushing your luck - but do what works for you!

    Unless the published literature about motor fuels is all bunk, the issues of volatility degradation and oxidation are real - not made up to sell fuel stabilizer.

    I think it's wise to pay attention to the recommendations about long-term storage made by engine manufacturers - and would rather err on the side of caution, esp. when the cost of doing so is so minimal.

  10. #10
    Vulture of The Western World Eric's Avatar
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    Re: Does gas really go bad?

    "And I am considering starting and running my BWM with it's four year old gasoline just to see what happens! "

    I'll be amazed if the tank isn't full of gunk and rust by now...


  11. #11
    DonTom
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    Re: Does gas really go bad?

    "Unless the published literature about motor fuels is all bunk, the issues of volatility degradation and oxidation are real - not made up to sell fuel stabilizer."

    Even if so, that does NOT mean that so called fuel stabilizer does anything to prevent such.

    There is so much of this going on. For an example, there was once an independent study done on RV toilet paper and how it biodegrades in RV tanks. That was when it was discovered one of the worse types you could buy was the most popular by RV'ers, which is sold in RV stores as being especially made for RV's. It was proved it was better to pay half the price and buy certain household brands, for a RV.

    And BTW, do you believe engine oils made for motorcycles are better in motorcycles than normal oils made for cars?

    -Don-

  12. #12
    DonTom
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    Re: Does gas really go bad?

    "I'll be amazed if the tank isn't full of gunk and rust by now..."

    In 1971, BMW was the only cycle manufacturer to coat the inside of their gas tanks to prevent rust. Besides, I left the tank full.

    Besides, the BMW gas tank is very easy to remove and clean. A five minute job.


    -Don-

  13. #13
    Vulture of The Western World Eric's Avatar
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    Re: Does gas really go bad?

    Quote Originally Posted by DonTom
    "I'll be amazed if the tank isn't full of gunk and rust by now..."

    In 1971, BMW was the only cycle manufacturer to coat the inside of their gas tanks to prevent rust. Besides, I left the tank full.

    Besides, the BMW gas tank is very easy to remove and clean. A five minute job.


    -Don-
    Ah, but what about your carbs?

  14. #14
    Vulture of The Western World Eric's Avatar
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    Re: Does gas really go bad?

    "And BTW, do you believe engine oils made for motorcycles are better in motorcycles than normal oils made for cars?"

    If you mean the oils made for high-performance sport bikes (many of which have operating ranges to 15,000 RPM) indeed I do.


    PS - Here's a quote from page 148 of my ZRX1200 owner's manual:

    "If left for a long time, the fuel will break down and could clog the carburetors."

    Not "might" or "could," but "will break down."

    Just fyi -



  15. #15
    DonTom
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    Re: Does gas really go bad?

    "Ah, but what about your carbs?"

    They are also easy to remove and take apart. I have Mukuni's on it, because the 1971 Bing carbs were junk that should have embarrassed BMW. As soon as the bike warms up, the Bings would not idle. And there is no known fix other than to replace the carbs. The old 1971 Bings only work well when they are cold to the touch.

    -Don-

  16. #16
    Vulture of The Western World Eric's Avatar
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    Re: Does gas really go bad?

    Quote Originally Posted by DonTom
    "Ah, but what about your carbs?"

    They are also easy to remove and take apart. I have Munkni's on it, because the 1971 Bing carbs were junk that should have embarrassed BMW. As soon as the bike warms up, the Bings would not idle. And there is no known fix other than to replace the carbs. The old 1971 Bings only work well when they are cold to the touch.

    -Don-
    Ah yes!

    Mikuni and Keihin (sp?) carbs are top notch...

    Still, why would you prefer havng to remove and clean the carbs to adding stabilizer prior to storage?

  17. #17
    DonTom
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    Re: Does gas really go bad?

    Not "might" or "could," but "will break down."


    Sure, in 20 years, no doubt. But did it say there was anything you could do about it?

    BTW, my 1971 BMW owner's manual says NEVER add anything to the gasoline or oil under ANY conditions.

    -Don-

  18. #18
    DonTom
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    Re: Does gas really go bad?

    "Still, why would you prefer havng to remove and clean the carbs to adding stabilizer prior to storage?"

    Which gasoline stabilizer says it will do more good than harm after four years of storage?

    -Don-

  19. #19
    Vulture of The Western World Eric's Avatar
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    Re: Does gas really go bad?

    Quote Originally Posted by DonTom
    Not "might" or "could," but "will break down."


    Sure, in 20 years, no doubt. But did it say there was anything you could do about it?

    BTW, my 1971 BMW owner's manual says NEVER add anything to the gasoline or oil under ANY conditions.

    -Don-
    Everything in the literature says gas begns to break down much sooner than that; read up on it for yourself. And I have to give weight to the recommendation/emdorsement of fuel stabilzer by so many engine manufacturers. These are not shysers hawking a product but the engineers who designed the engines, etc.

    Unlike, say, "transmission conditioner" or "motor honey" - products/additives you rarely, if ever, see endorsed by an automaker/engine builder, stabilizer is almost universally recommended for any vehicle when it will be left unused for more than a couple of months.

  20. #20
    Vulture of The Western World Eric's Avatar
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    Re: Does gas really go bad?

    Quote Originally Posted by DonTom
    "Still, why would you prefer havng to remove and clean the carbs to adding stabilizer prior to storage?"

    Which gasoline stabilizer says it will do more good than harm after four years of storage?

    -Don-
    Sta-Bil is the product I use; see their web site for more info....

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