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Winterization question- Full gas tank or Empty?


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You will likely get the same here as you have heard other places. There are those that fill to near full and those that leave near empty. Here's a couple of recent threads with some good info:

http://www.themalibucrew.com/forums/index.php?/topic/46280-marine-sta-bil-for-non-marine-engine/

http://www.themalibucrew.com/forums/index.php?/topic/46350-first-time-winterizing-drain-the-gas-or-stable-the-gas/

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Growing up with metal fuel tanks we always filled them full to avoid condensation in the tank. Now with plastic fuel tanks condensation is not an issue, so I leave as empty as possible with fuel treatment. That all being said - I have still heard arguments for either way....

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The condensation issue is behind us now with the plastic tanks. Now the issue is the effects of a winters layover on ethonhol laced gas. Even with sta-bil you run the risk of having a full tank (35-85 gal) go bad. You will hear both ways, I run mine as low as possible with sta-bil and then fill in the spring with fresh and some seafoam. My boat is a 2004 with over 700 hours and never a fuel related issue.

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I think it comes down to fuel quality. If you use fuel that may contain Ethanol than no. I'm told Ethanol fuel can breakdown is 3 months. If that's the case then all of the fuel should be drained at the start of each season, how many guys do that?

I've always filled my Camaro (20 years) and added Sta-bil but we have 94 Octane sold at Chevron that contains no Ethanol.

I tend to be a little on the lazy side and find it easier to fill the tank, add fuel stabilizer, make sure the stabilizer has made it to the engine and park it in a heated garage.

Who out there uses Fuel that contains Ethanol and drains there fuel system at the start of each season?

Who has had problems with there fuel degrading and costly repairs insued? If so, where do you buy your fuel?

The debate rages on

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I have some evidence to provide about how it doesn't matter. For the first 8 years of my boat's life I always filled the tank with fresh stabilized fuel for the winter. No problems.

Now for the last 7 years or so I've drained all the gas, then put 10 gals of fresh, stabilized fuel in the tank for the winter. No problems doing it that way either.

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I run mine to near empty, add stabil and run through the system. In the spring, I fill the tank with 10 gal of higher octane to help combat any potential issues. After that I run regular 87. It's been working fine for me.

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My thinking is if it doesn't matter then why would you fill it full for winter?

Sta-bil will prolong the life of gas but it still degrades. Why not drain it all the way or mostly and run stabil in the engine then fresh in spring?

That seems the most logical way to do it.

Because the old school way of thinking is that the gas tank will collect condensation inside it & dilute the gas with water. The emptier the tank is, the more water it'll hold. But I believe that the plastic tanks our boats have in them tend to collect condensation a lot less than the old metal tanks that boats used to have. While it could be true, it's really not the way everyone seems to think.

I had a little over a 1/2 tank in the boat yesterday. I dumped 7 oz of Stabil in it & took it out to ride yesterday afternoon. Now it's under 1/4 tank. If I don't ride any more at all, the gas in the tank & the fuel system has been treated. If we do ride, the boat needs gas & I'll treat it as I put it in.

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I just question what good you are doing by leaving that 1/4 tank in and running it in the spring. Seems like it should be drained if condensation is not a factor

I tend to agree. But the old school way of thinking is widely talked about, especially on other websites, other types of boats, etc. But even if the tank is empty, the fuel lines, pump & EFI should have treated fuel run thru them. And running these boats out of gas is HIGHLY not recommended. The pump is cooled by the gas & will die soon after. And their not easy.... or cheap.... to replace.

I was just reading on GarageJournal.com about this. One of the guys said that the Coast Guard frowns on pressurized fuel systems on a boat...... then continued his advice on how you should fill the tank, treat it, etc. I didn't want to get into it with him on all the details, just shook my head.

I'm no mechanic but I've been running these type of boats a while now & have never had a problem in the spring after treating the gas & running it low, then filling up with fresh gas in the spring.

Edited by Bill_AirJunky
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I tend to agree. But the old school way of thinking is widely talked about, especially on other websites, other types of boats, etc. But even if the tank is empty, the fuel lines, pump & EFI should have treated fuel run thru them. And running these boats out of gas is HIGHLY not recommended. The pump is cooled by the gas & will die soon after. And their not easy.... or cheap.... to replace.

I was just reading on GarageJournal.com about this. One of the guys said that the Coast Guard frowns on pressurized fuel systems on a boat...... then continued his advice on how you should fill the tank, treat it, etc. I didn't want to get into it with him on all the details, just shook my head.

I'm no mechanic but I've been running these type of boats a while now & have never had a problem in the spring after treating the gas & running it low, then filling up with fresh gas in the spring.

You make a great point about running the system totally out of fuel. Even further then pump damage, rubber and composite fuel components will dry out when out of the fuel. This is especially true with carburetors. For those that have to use ethanol blended fuel, I have no objection to running the tank low, but to run it and the fuel system dry for a season layup, could lead to damage.

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I just question what good you are doing by leaving that 1/4 tank in and running it in the spring. Seems like it should be drained if condensation is not a factor

Draining that 1/4 tank is a PITA. Leaving it is lazy, but convenient.

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I don't think you will ever see gas break down with the correct amount of stabil for the amount of fuel used within a 6 month period. I have personally used Stabil for many items that sit over the winter and I have never had bad gas when used correctly.

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I don't think you will ever see gas break down with the correct amount of stabil for the amount of fuel used within a 6 month period. I have personally used Stabil for many items that sit over the winter and I have never had bad gas when used correctly.

You are lucky. i have had bad gass isues before -- but somehow they are all related to copoius Mexican food consumption. I always thought Tequila was just like Stabil.

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I am no expert and not sure how true it is but I was told that a small amount of gas will go bad before a large quantity. It was recommend to me that I store with a full tank with stabil for less degradation.

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Yes, fuel spoils with or without a stabilizer in it, but a stabilizer will slow the process. 6 month old fuel will not create an issue or even pose any noticeable driveability problems, but to each his own. Phase separation due to ethanol blended fuel absorbing too much moisture is a separate issue, independent of fuel spoiling over time. Fuel can spoil with or with out ethanol and phase separation will take place as soon as too much moisture is absorbed.

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Yes, fuel spoils with or without a stabilizer in it, but a stabilizer will slow the process. 6 month old fuel will not create an issue or even pose any noticeable driveability problems, but to each his own.

And considering that dozens of us on this site alone do this every year without any issues........ well, practical experience says a lot.

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I fill my boats with FRESH gas, within a gallon or two from the top (want to leave room for expansion in the spring) and I stabilize with Startron Enzime, but we also run Startron in EVERY gallon of fuel we put in our boats within my skiing group to counteract the effects of the 10% ethanol around here...

we have been using Startron now for about 6 years

71gWeviaTfL._SL1500_.jpg

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  • 5 weeks later...

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