Winterization Fuel Storage

[Boilers2000]

For those of us that have to winterize what is your stance on the fuel tank. Do you empty it or fill it up. I can get mu head around filling it up and adding stability allows less air in the tank and less condensation that can build up as temps drop. I am only running ethanol free gas also.

 

[Grub54891]

It don't matter how full it is. Really no oxygen in there with the fumes. I store with whatever is there after the last run. Sometimes its near full, but never less than half a tank. I put sea foam in at the last fillup before the last run. No problems.

 

[QBhoy]

Full to the brim or as near empty as you can. Up to you. Also depends on your local climate. If there are big temp differences and humidity variances over the storage period...it’s essential.
I run mine as close to empty as I dare...then add a gallon of 20-1 mixed 2 stroke fuel. Then run it for a bit until it comes through. Then shut her down for the season.

 

[QBhoy]

It don't matter how full it is. Really no oxygen in there with the fumes. I store with whatever is there after the last run. Sometimes its near full, but never less than half a tank. I put sea foam in at the last fillup before the last run. No problems.

That’s maybe not great advice...regarding it not mattering how full it is and no oxygen with the fumes etc. That’s not quite how it works. It’s less to do with oxygen and more to do with moisture created by varying states of temps and humidity.
Not saying that sometimes you will get away with it...but not in all cases. Especially where I live.

 

[achris]

For those of us that have to winterize what is your stance on the fuel tank. Do you empty it or fill it up. I can get mu head around filling it up and adding stability allows less air in the tank and less condensation that can build up as temps drop. I am only running ethanol free gas also.

Dead empty or brim full. As the temperature is low anyway you don't have to worry about temperature sending the petrol sour. In the Australian north the problem is the opposite. At the height of summer, straight fuel has a lifespan of a few months, pre-mixed 2 stroke, about 4 to 6 WEEKS!

Laying up for winter my preference would be dead empty. That way, come spring, you fill up with the right blend for that particular time of year. Oil companies blend fuel to move the flashpoint and vapour point around, according to local temperatures. The last thing you need is trying to start a cold engine early in spring on 'summer' fuel...

Part filled is asking for a belly full of water come spring.

Chris......

 

[QBhoy]

Dead empty or brim full. As the temperature is low anyway you don't have to worry about temperature sending the petrol sour. In the Australian north the problem is the opposite. At the height of summer, straight fuel has a lifespan of a few months, pre-mixed 2 stroke, about 4 to 6 WEEKS!

Laying up for winter my preference would be dead empty. That way, come spring, you fill up with the right blend for that particular time of year. Oil company blend fuel to move the flashpoint and vapour point around, according to local temperatures. The last thing you need is trying to start a cold engine early in spring on 'summer' fuel...

Part filled is asking for a belly full of water come spring.

Chris......

Totally agree !

 

[Grub54891]

Well we have to disagree. I'm stored in all various fill levels, never get moisture in spring. Premium fuel only. If there is moisture getting in, its usually a leaking fuel cap, or improperly routed vent line. But what do I know. Only been storing my boats for 40 years. Northern Wi, Temps from 70° to -40, wet damp fall and spring.

 

[achris]

Well we have to disagree. I'm stored in all various fill levels, never get moisture in spring. Premium fuel only. If there is moisture getting in, its usually a leaking fuel cap, or improperly routed vent line. But what do I know. Only been storing my boats for 40 years. Northern Wi, Temps from 70° to -40, wet damp fall and spring.

I guess you're the exception that proves the rule.

To anybody else... This is NOT the way to do it. :facepalm:... Dead empty, or brim full... Never in-between.

 

[tpenfield]

The 'full tank' theory is just that. . . a theory, but un-proven. Think about it . . . with any amount of fuel in the tank, there is no way that 'air' can get into the tank, because, as we all know, gasoline fumes are heavier than air, and the space in the tank above the fuel level will be mostly gasoline fumes.

Air won't be able to come down the vent line, so outside moisture won't be able to get in.

Some boat/engine manuals are recommending to empty the tank. Fuel sitting for 6-8 months . . . nothing good can happen to it. (right?)

So, I usually empty the tank as best I can, but that usually leaves a few gallons of gas in it.

 

[achris]

This will be true while the temperature doesn't change. But as the temperature rises, and the liquid fuel expand it forces some of the fuel vapour out of the tank, via the vent line. Then when the temperature drops the liquid will contract, drawing air (laden with moisture) back in through that same vent line. When the moisture in the air then hits the fuel surface it will be adsorbed into the fuel. The next heating and cooling cycle will cause it all to happen again. Gradually water builds up in the bottom of the tank and come spring the pump is sucking water not fuel....

Chris....

 

[Lowlysubaruguy]

I’m an empty as possible tank believer. I did my own test over a number of years.

Test boat has 4 brrl carb 37 gallon tank boats covered in sunbrella if that matters stored outside high temp and humidity swings and the fuels here in the northwest have at least 10 to 15% ethanol. Some winters it sits with a foot of snow on it for months some it’s warming and freezing daily if the weathers close to the freezing point. Put up in October usually back in the water early may sometimes March or April if I salmon fish for springers.

Full tanks left me with a full full tank of fuel that ran mediocre under power hard starting and stalling at idle worse cold

five to ten gallons left me with that much fuel to burn off probably worse than full but less to get through easier to cut with a few gallons of new fuel each spring

today i disconnect the fuel line at the carb and power up the fuel pump and empty the tank I’ve tapped into the wire to the fuel pump so it’s really easy now pull a car up to it and pump it dry.

I replace my fuel filter after running about ten gallons through it and never have any issues.

 

[Scott Danforth]

With an open vented tank, doesnt mater how full it is.

Any temp change will allow the system to breath in or breath out. Every time the system pressure drops, fuel evaporates.

I personally prefer to empty the tank

 

[tpenfield]

Who’s got an old fuel tank lying around? Winter is coming, perhaps we can put this to a test.

 

[dingbat]

I boat 9 to 10 months (March - December 31) out of the year.

Over the years, I’ve stored anywhere from a full tank (94 gallons) to as little as a 1/4 tank (25 gallons). Anywhere from 3/8 to a 1/2 tank is typical.

On what is perceived as being he last trip of the year, I dump a bottle of Stabil in the tank when I fuel up in the morning. Well mixed and pumped through the fuel system by the time we get back to the dock.

Come Spring, top off the tank with 93 octane E10 and go boating.

 

[achris]

Who’s got an old fuel tank lying around? Winter is coming, perhaps we can put this to a test.

Don't need an old tank to know what happens... If I fill my tank when it's 20 degrees, when it hits 30, the wife is complaining she can smell petrol. I lose about a litre in overflow from the vent ... And I have a liquid return system on the vent line. So that's all the air/vapour plus a litre of liquid being forced out just through thermal expansion... And that's only 10 degrees rise....

Chris....

 

[achris]

Just looked up and found the value for the coefficient of expansion of petrol. 0.000950/K

For my 180L tank and just a 10 degree variation, that's 1.71L...

Chris....

 

[tpenfield]

Just to throw some more 'gasoline' on this fire . . . Some folks who fill their fuel tank and then put the boat away for storage find that fuel overflows out the vent.

In addition to the thermal expansion, which can be significant, there is also the vapor pressure that builds in a fuel tank. The pressure can also force fuel out of the vent, if the boat is sitting in such a way that fuel is at the vent fitting within the tank. or if the tank is over filled, etc.

I also think it is the vapor pressure (fuel evaporation) that keeps an abundant amount of moisture laden air from entering the tank as the outside temperature rises and falls.

 

[Ncherry84]

Me personally, always full with non ethanol premium and I prefer star tron enzyme fuel treatment. It varies temp wise from mid to upper teens to as low as -50F here in the winter time, sometimes in the matter of 24 hours. Usually stored from October/November until April/May sometimes even June. Never had an issue and my past boats have always fired right up 0 problems in the spring time on the first start after closing all my water drains and blowing the fogging oil out of the motor.

My $.02 cents.

 

[HT32BSX115]

Who’s got an old fuel tank lying around? Winter is coming, perhaps we can put this to a test.

Yeah. Someone already did that test. He found that condensation is an old wives tale.....

https://www.yachtsurvey.com/myth_of_condensation_in_fuel_tanks.htm

If you're worried about gasoline going bad, store it near empty. If you're worried about fuel left in the tank, put snake oil in it.

If it sits for less than a year, don't worry about it at all.....

Cheers,

Rick

 

[wellcraft-classic210]

After recently fixing a small engine with old ethanol fuel -- I was surprised to see how corrosive and destructive it was.

Not sure how long it takes for fuel to become " old and corrosive under various conditions " but I can say its worth avoiding.