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  1. #1
    Petty Officer 1st Class
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    Default Winter storage: fuel tank full or empty??

    Hello,
    This is our first time with a built-in gas tank and I'm wondering what is the best way to store it for our long Maine winter: full, empty, or in between?? Thanks,
    John

  2. #2
    Petty Officer 1st Class Lakes84's Avatar
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    Default Re: Winter storage: fuel tank full or empty??

    I was always taught to filler up...less condensation that way. Make sure you put Stabil or Seafoam in the gas to keep it fresh. Ensure it's in your whole fuel system. Opinions on this will vary, trust me, but that's how I've always done it with no problems.

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  3. #3
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    Default Re: Winter storage: fuel tank full or empty??

    Fill it up an use stabil in the fuel the run your engine just long enough to run the fuel-stabil mix through your fuel pump and fuel lines.

  4. #4
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    Default Re: Winter storage: fuel tank full or empty??

    Empty that way you start off with fresh fuel next time.
    Do you get condensation in your car fuel tank if it's not full?
    Opinions on this will vary, trust me, but that's how I've always done it with no problems.
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  5. #5
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    Default Re: Winter storage: fuel tank full or empty??

    no easier way to start a holy war than 'empty or full gastank'!

    In all honesty neither method is more right than the other. I personally get it as low as possible. Even with stabil, gas can go bad. The less that is the tank, the better, as I can just mix in new stuff in the spring.

    I CAN say from years of experience, snowmobile gas tanks are absolutely always empty. Because they are stored during the summer, the reactions that happen to cause gas to go bad are sped up. Even with stabil, the stuff left in the tank by the next winter is generally bad. Carbs are usually removed and cleaned yearly on snowmobiles. Boats aren't as affected because of temperatures during storage.

  6. #6
    Supreme Mariner oops!'s Avatar
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    Default Re: Winter storage: fuel tank full or empty??

    here we go.....full......the condensation in the tank will collect.....i have heard the myth that tanks will not get water in them thru condensation.....but its not true....just ask a pilot. they actually have a tool for checking if there is condensation in the fuel tanks. ....and yes....water does get in there.

    dont forget the stabil
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  7. #7
    Lieutenant Junior Grade 90stingray's Avatar
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    Default Re: Winter storage: fuel tank full or empty??

    Quote Originally Posted by oops! View Post
    just ask a pilot. they actually have a tool for checking if there is condensation in the fuel tanks.
    You think a pilot would actually use it??? they never do... they dont want to get all smelly
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  8. #8
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    Default Re: Winter storage: fuel tank full or empty??

    Quick, someone call Mythbusters!

  9. #9
    Chief Petty Officer mpdive's Avatar
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    Default Re: Winter storage: fuel tank full or empty??

    I'm staying out of this one. Been there done that. This is one step short of starting an ethanol debate.
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  10. #10
    Admiral smokeonthewater's Avatar
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    Default Re: Winter storage: fuel tank full or empty??

    yep store it full OR empty..... either will work..... half full is begging for condensation tho

    An empty tank will get condensation in it when temps fall but it will just evaporate when they rise..... the partial tank tho traps the condensation under the gas and keeps it from evaporating..... thus it builds up
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  11. #11
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    Default Re: Winter storage: fuel tank full or empty??

    i store my sleds full, and start them monthly, never had a problem. only cleaned the carbs once in 8k miles (4 seasons) and they werent dirty.............boats with an inboard tank i also store full, stabilized, never had an issue.
    ive had a tougher time starting a sled that was left dry all summer then one left full. never had a fuel issue.

  12. #12
    Commander chriscraft254's Avatar
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    Default Re: Winter storage: fuel tank full or empty??

    I leave mine full, in my mind it is better than leaving more space for moisture/condensation to accumulate. I do try and get it really full so there is very little room for condensation. Stabil or Seafoam as already mentioned. Plus gas next year will probably be more expensive!

  13. #13
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    Default Re: Winter storage: fuel tank full or empty??

    What ever is in it at the end of the season is how it is stored, lawn mower, snow blower, boat , powersaw, whatever, I never use stabilizer and have had no problems, been doing it this way for over 40 years.
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  14. #14
    Lieutenant Junior Grade DuckHunterJon's Avatar
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    Default Re: Winter storage: fuel tank full or empty??

    I've always stored everything full, with Seafoam added. Maybe right, maybe wrong - works for me.
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  15. #15
    Chief Petty Officer '78 Crusader's Avatar
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    Default Re: Winter storage: fuel tank full or empty??

    Quote Originally Posted by 90stingray View Post
    You think a pilot would actually use it??? they never do... they dont want to get all smelly
    I'm a Commercial pilot, been flying for a living for years and I check the fuel tanks for water before the first flight of the day and after each fuel stop. Yes, water DOES get into the fuel tanks through condensation......this is a fact and not really a debatable topic....it happens and will continue to happen.

    With that said, the ethanol based fuels do break down sooner than the "real gas" did prior to the introduction of ethanol. At one time I stored my fuel tanks full of fuel....however I've changed my practices since the introduction of ethanol....I now drain the tanks as low as I can get them and then put in some seafoam / stabil and call it good.

  16. #16
    Chief Petty Officer jmarty10's Avatar
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    Default Re: Winter storage: fuel tank full or empty??

    Always stored witha 1/4 to 1/2 tank with stabil, hasnt been a problem for the past 5 years. Aint a lot of condensation in the fall, winter and early spring anyways in the North. Filler up in the spring, change water seperator and go boating.
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  17. #17
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    Default Re: Winter storage: fuel tank full or empty??

    I store mine full with plenty of Marine Sta-bil. It's always a bonus to have have a full tank in the spring, and, if there's ever a long power outage during the winter I have 70 gallons of fuel for the generator.
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  18. #18
    Petty Officer 2nd Class kylejb2663's Avatar
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    Default Re: Winter storage: fuel tank full or empty??

    Quote Originally Posted by oops! View Post
    here we go.....full......the condensation in the tank will collect.....i have heard the myth that tanks will not get water in them thru condensation.....but its not true....just ask a pilot. they actually have a tool for checking if there is condensation in the fuel tanks. ....and yes....water does get in there.

    dont forget the stabil
    I'll Agree with you Oops! I am a private pilot (in training), I have about 35 hours under my belt.

    We ALWAYS check both gas tanks to make sure we do not see water in the tanks and it has happened before!! It's part of a preflight checklist that you learn to love because it saves your @$$. Tanks are both full and you still get condensation...

  19. #19
    Fleet Admiral Mark42's Avatar
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    Default Re: Winter storage: fuel tank full or empty??

    I store empty. Never had condensation issues. Never any water in the water filter either.

    Regarding airplane tanks, yes they do get condensation, but that is due to the quick changes in altitude, air density, temperature and humidity that they experience. Boats don't do that.
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  20. #20
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    Default Re: Winter storage: fuel tank full or empty??

    It's a controversial subject for sure. Comparing it to an automotive fuel tank is not correct since automotive fuel tanks (since the introduction of Ethanol) are pressurized to keep condensation out. I boat all year round but there are months when nasty weather takes the fun out of it so mine can sit for a month at a time. I have a Perco vented fuel cap that does a very good job at keeping moisture out and I keep my tank full during the winter months. I always store my boat inside and use recommended amounts of Stabil Marine additive with every fill up. If you have standard fuel vent, some folks say that taping it off during storage keeps the moisture out but on other boats, I lengthened the vent hose and put a loop in it so that it acts like a P-Trap when the tank is full. As the tank level drops the trap opens up. I never had any problems with fuel flow but some might be leary of that and I can see why. Like I say, it didn't effect my engines need for fuel.

    Just my .02

  21. #21
    Lieutenant Commander paultjohnson's Avatar
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    Default Re: Winter storage: fuel tank full or empty??

    21 yrs storing my boat, snowmobiles, ATV and with 1/4 tank or less of non oxygenated premium. Never had a fuel system problem. Filters are always spotless. I am lucky to have a gas station close by that sells non-ox prem. My 2 Cents. Store plastic tanks low , metal tanks like my 77 cutlass full to minimize surface exposed to air, moisture and resulting rust.
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  22. #22
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    Default Re: Winter storage: fuel tank full or empty??

    I leave mine 9/10 full of premium w/ Stabil, because the biggest issue is loss of octane over time and when I use Stabil my engine starts much faster.

    It sat near empty one year and I had no issues. ::shrug::

    I've read that condensation issues are overblown, but part of me just puts faith in the boating crowd so I go 9/10 full.
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  23. #23
    Lieutenant Commander 109jb's Avatar
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    Default Re: Winter storage: fuel tank full or empty??

    A few points.

    Modern car gas tanks aren't open vented anymore, so any comparison between an open vented boat tank and a car is not valid. Car gas tanks are actually pressurized, which is why you hear air escaping when you remove the fuel filler cap on your car. No direct vent to the outside air and no condensation.

    Water can condense in an open vent gas tank. Airplanes see changes in altitude, true, but the altitude doesn't change in the hangar. Saying it only happens because of the changes in altitude is false. I have seen it from direct experience. The longer they sit the more water they have. Unlike ethanol blend fuel, aviation gas can't hold anywhere near as much water in suspension and the water separates out easily. The separated layer though is just water, not the ethanol-water mix. On my airplane, I try to store it with full tanks. On those occasion where the fuel supplier isn't open when I come back from a trip, I put it away with partially filled tanks. On those occasions there is almost always at least a little water in the fuel when I sump the tanks. When left full there is never any water. And yes, pilots are trained to check the fuel sumps for water before the first flight of the day and after every fuel fill.

    Ethanol fuels will absorb some water up to the point where they separate. The key is to keep the ethanol fuel from absorbing enough water to separate. Hence one of the reasons cars don't have open vent tanks anymore. IMO, keeping the tank full is the best way to do this as there is less room for condensation, and there is more fuel to absorb more condensation if it does occur.

    I have 4 snowmobiles in a trailer in my back yard right now. During the season I run 87 octane as that is what is specified for all my sleds. For storage, I fill them up with high octane fuel and add a fuel stabilizer. I run the engines enough to get the stabilized fuel throughout the system and then I fog the engines. I do shut off the fuel valve and drain the carbs though. I have one fuel injected sled and that one I just run it through the system and fog. No draining of the fuel system. I don't start them again until the following season. Never had a problem with condensation, or separated fuel or poor running from octane loss, and all I can get near me is ethanol blend fuel. Incidentally, this is the same procedure I use for my boat.

    For my boat, as already stated, I fill the tank because a full tank has less room for condensation. Also, most fuel tanks you can't get all of the fuel out of anyway. There is always a little left behind. If that 1 or 2 cups of fuel in there is ethanol blend then it won't take much water to cause separation. Unlike non-ethanol fuel, the separated layer is not just water, but an ethanol-water mix that is somewhat caustic.

    As I said, for me I fill the tanks and stabilize the fuel, run it long enough to get it through the system, and then drain the carbs if carb equipped.

    Everyone needs to make their own decision as to what they want to do. I'm just stating my reasoning and what has worked for me.
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  24. #24
    Supreme Mariner bruceb58's Avatar
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    Default Re: Winter storage: fuel tank full or empty??

    When this subject comes up I always like to post this.

    http://www.yachtsurvey.com/myth_of_c...fuel_tanks.htm
    I agree that water getting into the fuel tanks is caused by either the cap leaking or it was delivered with water in it.

    I just leave my tanks wherever they are and never worry about it. I have yet to see any water in my water separating filters.

    As far as cars having closed fuel systems, has everything to do with emissions.
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  25. #25
    Petty Officer 1st Class Lakes84's Avatar
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    Default Re: Winter storage: fuel tank full or empty??

    Quote Originally Posted by Jerryh3 View Post
    I store mine full with plenty of Marine Sta-bil. It's always a bonus to have have a full tank in the spring, and, if there's ever a long power outage during the winter I have 70 gallons of fuel for the generator.
    What I great idea...I would have never thought of that!

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