Gas during winter season

hanzelvh · November 2014

I was used to fill off my dieseltank 100% before putting in winter storage, but now I changed to gas.
I heard that gas is loosing power after few months of storage.
To have 500+ liters of gas with less power is not attractive.
What is your experience?

MarkB · November 2014

I use to add stabilizer and fill my tank full before winterizing worried about condensation, but then would go months in the next season with that old gas. The stabilizer helps, but I can tell you first hand it's not like fresh gas. Get fumes, etc coming off the engine. Fresh gas no problem. And condensation in the tank, we'll that's what the water filter is for. So I now keep it empty and fill up with fresh gas the next season.

Michael T · November 2014

On Mercury's new website and my experience has been to add fuel stabilizer and a fuel lubricant additive, fill the tanks "to the top" with non-ethanol fuel (to avoid phase seperation). I run the engines until hot - which puts the stabilizer and lubricant throuhout the engine and at the same time heats the oil to 165 or more degrees F before the oil change. This also drops the fuel level in the tanks enough to reduce the potential for spillage in the Spring when the fuel heats up a bit and uexpands. BTW fuel tank expasion doesn't happen as much with cruisers as with smaller boats as cruiser's tanks are lower in the boats and not as exposed to heating as the tanks in smaller boats. To be extra safe I do put an absorbent sheet under each fuel fill cap to catch any spillage in the Spring. In my opinion the potential to get water in your tanks due to condensation when empty or nearly empty (actually never really empty as you can not do that nor would you wantn to ever totally empty them) is far worse that some gas seepage or maybe and I say ]maybe having 90 octane degrade to 87 octane - and even if it did it would still be 100% fine and would not have phase seperated as there was no ethanol in it. As well, my fuel tanks are aluminum and they should never be left empty for any length of time.

MarkB · November 2014

MT what % water would be produced degrading to 85 octane?

MarkB · November 2014

And given the density of water shy wouldn't it coallate and collect at the bottom of the tank as opposed to maintain a fine suspension in the gas. I think we are making too many assumptions here.

Michael T · November 2014

Mark, in my opinion, even if 90 octane (non-ethanol/methanol, of course) did degrade to say 87 octane and I doubt it would degrade that far), it should not phase separate. If the tanks are full the chance of condensation forming is reduced by 95% (conservative estimate, I'd say). You are correct in that when phase separation occurs in a marine gas tank the water does accumulate in the bottom of the tank and stay there until it gets stirred-up. I have watched as water was pumped-out of a crusiers's gas tanks after phase separation. It was unbleievable. Of course the operator pumped from the bottom up. Expensive, but better than detonating your engines. If you ask marinas to be honest as to why they don't want you to top off your tanks its because many boaters think topping-up their tanks means filling them up until the gas is running out the cap or in older boats spitting out of the gas vent. Worse yet, some owners fill their tanks up after they have run them to heat up the oil, so the gas is right up the fill tube. That's too full and worries marinas (justifiably) for environmantal, safety and insurance purposes. Of course, we all have our personal ways of doing things and from what I have read and experienced the process I have followed has worked well for me. Since hanzelvh asked for opinions that's mine. MT

raybo3 · November 2014

I took my boat out of the water for the winter yesterday. I had about 1/8th of a tank. I told the marina to pump it dry. I dont want any problems in the spring......

LaRea · November 2014

This topic comes up every season, and there seems to be no clear answer -- even at BoatUS. See these two conflicting articles:

http://www.boatus.com/seaworthy/ethanolwinter.asp

http://www.boatus.com/pressroom/release.asp?id=842#.VFffPvnF9V0

One article says to definitely fill the tanks. The other says that empty is good, and full is good, but you should pick one or the other rather than leaving it half-full.

How's that for a non-answer?

Stodge · November 2014

I normally put my boat away with around 1/2 tank and make sure there is enough Sta-bil in there to treat it. So far, so good.

JC290 · November 2014

RY do you treat your diesel?

raybo3 · November 2014

I have left my tanks half full, empty and full. Never had a problem. Make sure you treat if with startron (blue stuff) and you should have no problems.

Michael T · November 2014

I 'm not sure how fiberglass/plastic tanks react but if you leave an aluminum tank out in colder climates condensation will form on its interior walls and collect in the tank - how much I'm not sure. It would certainly depend on the temperature swings. Since my 360 has aluminum tanks I fill them for that reason. Of course, phase seperation should not occur with non ethanol fuel. Non ethanol fuel is rumoured to become "stale" over a winter lay up. I bet 3 people have 6 versions of what that means! Anyway, I guess that's why we use fuel stabilizer?! There is a fair bit os skepticism about fuel additives. That noted, Istill use them. I use startron and a new fuel lubricant sold at W.M. I figure for the cost it's cheap insurance. When I trailerable boats I used to go to a Sunoco and put 94 in the tank for the winter. ;-) MT

raybo3 · November 2014

I left my power washer in storage for 3 years and with a half full tank. Took it out and after 4 pulls ran like a top. I did not treat the gas. Go figure.....

hanzelvh · November 2014

thank you all for your opinions, however I still do not know what is best

raybo3 · November 2014

TREAT the gas and put the boat away..... You will be fine....

racingricka87 · November 2014

I never treat my fuel. I always find its best to fill your last two tanks of the season with 93 octane to the top. I have let one of my boats sit for 3 years and ran that old gas in her had zero issues. If you do have gasvpumped out just run it in your lawn mowers and or vehicles.

racingricka87 · November 2014

this goes for all my toys fyi right now I have 20 gas powered things that sit for 3-6 months at a time. Only time I had a issue was when I tried draining gas out of carb and letting it sit then it got all gummed up and seals shrunk. 10 years i have done it like this

Michael T · November 2014

Best choice: fill-up with NON-ETHANOL gas and treat it with Startron and a lubricant, fill-up your tank(s) and relax. The higher the octane rating, up to 94 the better. If you put ethanol gas away in a partially filled tank you WILL get water in it. Gas treatments will help non-ethanol gas stay "fresher" and "may" slightly mitigate some phase seperation aspects of ethanol fuel. This is not an "opinion" this is a chemical fact: If ethanol fuel (and by this I mean 10% ethanol fuel or worse 15% ) is left to sit - phase seperation begins at about two weeks and increases as time goes on. If you can only get ethanol based fuel I would pump the tank out before storage or have it polished in the spring. If you can get non-ethanol fuel I'd treat it and fill the tanks. MT

raybo3 · November 2014

MT non-ethanol is not a choice for me. I put star tron and never a problem

LaRea · November 2014

Here's my strategy, which I have used successfully since 1998.

First, I start with solid research and good intentions. Then, I continue using the boat until the weather is ridiculously cold and all nearby fuel docks are closed for the season. Then I winterize the boat with whatever fuel happens to be in the tank. If my mechanic has a couple bottles of fuel stabilizer, he dumps it into the tanks. Four months later, I de-winterize the boat and everything is fine.

hanzelvh -- the method Michael T described is probably better.

MarkB · November 2014

Guys this is going to be a longer than usual post, but all the FACTS are here, so spend the time and read it.

STORING YOUR BOAT ON AN EMPTY TANK

First off, let me refer you to a website which has the MAX water content of air at various temperatures:

http://www.engineeringtoolbox.com/maximum-moisture-content-air-d_1403.html

So you will see at 86F, the max moisture content (100% humidity) is 30.4 g/m3.
You will also see at 14F, the max moisture content is 2.31 g/m3.

I would call this a worst case scenario - somehow 100% humid 86F air completely filled your gas tank and all the air in that tank was cooled to 14F.

This means that a maximum of 28.1g of water could condense out per cubic meter of tank volume. My tank is 285L, or 0.285 cubic meters. So at most 8 g of water could condense if I had EVERYTHING working against me. That is 1.5 teaspoons of water.

STORING YOUR BOAT ON A FULL TANK

Now for the other alternative - you have to look at two scenarios (1) storing ethanol containing fuel, and (2) storing "ethanol-free" fuel (in brackets because "ethanol-free" doesn't necessarily mean it is free of ethanol, but meets a minimum standard.

I am going to refer to this paper, for details - it's a good read if you have time:

epa.gov/oms/regs/fuels/rfg/waterphs.pdf

1) Ethanol containing fuel. This is about the worst scenario possible. See this website:

http://ttypes.org/ttt2/ethanol-blended-fuels

The problem is phase separation. If there's enough water (at 14F it needs to be higher than 0.35% water by volume), then every 5 gallons of fuel turns into 1/2 gallon of alcohol/water mixture, of which 1/4 is water and 3/4 is alcohol. That's 2.5% of the gas turning into water! In my tank, if it was full (285L), I would need around 1L of water in the fuel before phase separation would occur at 14F, then it would make over 7L of water!! Boom!

However, note that we calculated above that an empty tank can only produce about 8 mL of water, so that's not enough to cause phase separation for a full tank (and you wouldn't get that much condensation to begin with anyhow with a full tank). Not on it's own anyhow. I would say it's only a problem if the gas has been in the tank for a long time and has already absorbed lots of water from ambient, and it only needs that last 8mL to push it over the edge.

Verdict - I wouldn't keep the tank completely empty, as doing so (a) increases the amount of condensation, and (b) with less gas in the tank, it takes less condensation for phase separation to occur. On the other hand, if you have a full tank and can't consume it quick enough, you actually increase the chances of phase separation, as water will absorb over time (over many months). Don't take my word for it, but I would probably leave 1/2 tank of gas, unless I knew I would consume more in the first month after coming out of storage. Note, some sites do talk about concern of gas tank corrosion if phase separation does occur - so really you want to avoid this. The most important thing is to stabilize that gas, and use it as quickly as possible to avoid phase separation. I personally would be more worried about not using that gas for a long time, as that is the biggest risk of phase separation.

2) "Ethanol-free" fuel
Pure gas does not have the ability to absorb water (well not that much). In essence, when it reaches it's water saturation point, then any extra water just won't absorb and it settles out. It doesn't phase separate (at least that's what the sites I have read have said).

So essentially the water you will get in the gas is the water it can't absorb. If the gas was saturated with water, and the tank was essentially empty, then that means about 8mL of water in 285L can be water. I'd imagine if you fill the tank with fresh gas in the spring, some of the water would re-adsorb into the fuel, and the turbulence would disperse it fairly quickly.

I can tell you first hand that last winter I stored with a full tank of ethanol-free fuel, added sta bil as well, and I basically didn't have to fill my tank all that much this summer (didn't do enough boating). I did notice more black fumes from the exhaust, especially on starting the engine. There was also some minor carbon deposits on the water surface (not a lot, but it was different to last year, when I had fresh gas).

Verdict - chances of a water problem are a lot less with ethanol-free fuel. This small amount of water (8 mL at most) the fuel/water separator will easily handle that, especially because it won't come in as a slug (not that little in so much fuel). Still stabilize the gas, as "ethanol-free" fuel may not be totally free of ethanol. In my opinion, I don't see a big issue having the tank 1/4 to 1/2 empty. If you plan on consuming a full tank in the first month after it comes out of storage, then sure, I would go ahead and fill the tank.

MarkB · November 2014

RinkerYan said:

Do you know how long it takes to separate?

It separates when enough water has been added. The water is absorbed by the fuel from the environment. If some rain gets in (open fuel cap), then it can happen in minutes to hours.

LaRea · November 2014

Great post!

I'm guessing the tank "breathes" over time. Moist air comes in, gets cooled, sheds water into the fuel, and then more moist air comes in a few days or weeks later. But the real key is -- to keep your boat healthy, use it often!

MarkB · November 2014

LaRea - exactly, use the gas quickly. And that is my main point. You have a better chance of things going wrong with a full tank that takes 1 year to be consumed, than a 1/2 full tank that takes 1 month to consume.

Michael T · November 2014

Re: Emptying your gas tanks for winter storage. I wanted to check first before posting. I remember my friend's dad welding near the gas tank on his 73 corvette. He filled the gas right full before he started. We were amazed, and asked him why. He said - full tank won't explode, empty tank will. I have always believed that the empty gas tanks were by far the most dangerous - that's our high school chemistry at work, right? Anyway, I called a friend who ownes two insurance brokerages. He got back to me this morning. His reply was fast and decisive. He said ":Empty the tank of any boat that has a fixed-in-place tank and you have no insurance coverage or liability coverage, of any kind, with any of the insurance carriers I do business with. If this caused damage to your garage, house, other stored boats or a marina you would face all of the costs - none insured by my companies". He's a life long boater whose father used to own one of the biggest marinas around. He said, "Michael, why are you asking? You know the drill - fill your tanks, add fuel stabilizer, run the engines to hot and change the oil." I explained why the questions. He replied "If a customer stored a cruiser with empty tanks and it exploded (remember the ratio 20:1) I'd thank him for letting the insurance company off the hook for coverages/payments. MT

MarkB · November 2014

So, does that mean every time our tanks reach 5% before we fill up, we are not insured? Sounds like BS to me. No offense MT, I know you are passing on info, but how could they possibly use a stupid rule like that? A gas tank 1/2 full is as dangerous as a gas tank that is empty. The fuel/air mixture above the tank IS DIVISION 0 Explosion Classification. I do this for a living. The systems must be designed in compliance with this, which means the fuel sending unit which is submersed in the tank must be DIV 0 compliant (spark proof, static proof, etc). In my experience, as the tank level varies, the classification does not change. This would be news to me, if an insurance company now declares it does, as this is not how it is done on our projects involving the storage of flammable liquids.

MarkB · November 2014

And even if the insurance makes a rule like that I would ask two things:

(1) to show me in my insurance policy where that particular exclusion is written up, and
(2) to prove to me that an empty tank is materially more dangerous than a 1/3rd a full tank (which is the general guideline adopted by mariners globally for a safe minimum level).

There's no way they could prove this, because it isn't true, in my opinion.

Perhaps we should all be asking our insurance companies the same questions.

TonyWalker · November 2014

Just a question. An empty tank with fumes can be cajoled into exploding. But the energy released is limited to the fumes energy. If it is half full or more, I would think the fire would last a lot longer. I guess there is a question in there somewhere.

Tony
Salt Shaker 342

MarkB · November 2014

Tony, I am pretty sure a spark above a half full tank would still cause an explosion. I would assume there's enough air in there to ignite. After the explosion though, as you point out, you still have all of that liquid fuel, which would have dispersed everywhere around the boat from the explosion, and now be burning things down rather quickly (or at least what is left of the boat).

Anyhow, this may have to remain theory, as this is one test I'm not prepared to do.

LaRea · November 2014

There's nothing in my boat policy about fuel tank levels, but -- this is a reason why every boat owner should consider adding an umbrella policy. If your boat insurance doesn't cover a loss because of some obscure exclusion, the umbrella policy will.

A $3M umbrella policy costs about $150 a year.

MarkB · November 2014

Now that's a good point LR.

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