Winter Storage Ethanol "Myths"

[smoothmove]

BoatUS has an article in their latest pub talking about living with ethanol enhanced gasoline blends and specifically talking about storing over the Winter. While I'm glad to see the effort made to enlighten the reader, it's a lot of the same ol' "Do I store with the tank full or empty?" discussion that never seems to advance past the speculation stage. I am suspicious of the claims that large amounts of water can be "breathed" into a tank by repeated expansion and contraction. If you spend some time with a paper and pencil and do some projections with temperature and expansion rates, it's hard to come up with a scenario that would cause significant problems. Toward that end I set up a little experiement last Winter using some desiccants to examine the problem a little. You may find it interesting.

http://www.wacolab.com/ej/gasdriers.pdf

Eric

 

[sgharford]

Just like myth busters - good for you and thank you for posting! Psychrometry in action. I'm wondering - is it mostly the expansion and contraction of the fuel or of the air that causes the 'breathing'? You made mention in your experiment that you tanks were pretty much empty, so if the fuel causes most of the breathing then a full tank would cause even heavier breathing and perhaps be worse than a empty tank to boot.

 

[smoothmove]

I'm wondering - is it mostly the expansion and contraction of the fuel or of the air that causes the 'breathing'? QUOTE]

It's the air - or maybe I should say gasses. The density of the fuel of the fuel is pretty constant over the temperatures we are dealing with.
ej

 

[TopHattandTails]

Always a great debate for a few of us locally. The temps in Ohio range between -10 F to +40 F typically in the winter, with most usually hovering around the freezing mark. Big temp fluctuations are very real and possible between night and day times. Storing inside with heat myself, the best argument I've heard to "full or empty tanks" is that with empty tanks the risk of explosion are reduced. Fresh fuel in the Spring would be my only reason, but to each their own. Of course full tanks allows a spur of the moment ride in case the weather is nice before haul out!

 

[SKYCHENEY]

I base my empty or full decision on price speculation. If I think diesel will be higher in the spring, I try to top off before winter. If I think it might be less in 5 months, I leave them where they are.

Sometimes I win and sometimes I lose. But, when I'm running around for the first half of the summer on "cheap" fuel, it makes me feel good.

 

[sgharford]

This definitely sparked my interest (I saw that article in Boat US last night too). I found a 'google source’ that stated "The standard coefficient of gasoline’s expansion/contraction equals 0.069 % per degree Fahrenheit". I found from another 'google source' the coefficient of expansion for air to generally be accepted as 0.2035% per degree of farenheit (it changes with actual air temp). So you’re right, looks like air expansion/contraction beats fuel expansion by about 3:1.

So, a full tank does in fact cause less breathing. Curious, what climate was your boat in when you ran experiment? Hot air can carry more water then cold air. Warm days and cold nights (higher delta T), would cause more expansion and contraction. So if in warm, humid climate where days are very warm and nights are cool/cold their cold be enough action going on to make condensation a problem, especially given enough time.

I guess it really comes down to saturating the air with enough moisture during the day time(s) so that at night the walls of the tank and/or fuel surface cool below the dew point temperature of air in the tank. Given enough breathing time, seems plausible in a humid climate like Florida where the winter nights can get pretty chilly as well. Then the question becomes, just how much water is actually added (in a place like Florida) and now much water is detrimental to fuel supply? Thought nifty how you used the desiccant to measure water content.

 

[smoothmove]

This definitely sparked my interest (I saw that article in Boat US last night too). I found a 'google source’ that stated "The standard coefficient of gasoline’s expansion/contraction equals 0.069 % per degree Fahrenheit". I found from another 'google source' the coefficient of expansion for air to generally be accepted as 0.2035% per degree of farenheit (it changes with actual air temp). So you’re right, looks like air expansion/contraction beats fuel expansion by about 3:1.

So, a full tank does in fact cause less breathing. Curious, what climate was your boat in when you ran experiment? Hot air can carry more water then cold air. Warm days and cold nights (higher delta T), would cause more expansion and contraction. So if in warm, humid climate where days are very warm and nights are cool/cold their cold be enough action going on to make condensation a problem, especially given enough time.

I guess it really comes down to saturating the air with enough moisture during the day time(s) so that at night the walls of the tank and/or fuel surface cool below the dew point temperature of air in the tank. Given enough breathing time, seems plausible in a humid climate like Florida where the winter nights can get pretty chilly as well. Then the question becomes, just how much water is actually added (in a place like Florida) and now much water is detrimental to fuel supply? Thought nifty how you used the desiccant to measure water content.

FWIW My little test was done in an unheated barn over the 2007/8 winter.
Your questions are all good and answers could certainly be developed with the proper experiments or calculated by a clever engineer for that matter, with variables for humidity, temperature, time et cetera, but like everyone else here, I have better things to do with my time - like earn a living. Guess my real point is that it doesn't really seem like BoatUS is plowing any new ground by going around and talking to people regarding their opinions. Maybe they could conduct a little research or do some careful thought instead.

ej

 

[sgharford]

I think your experiment is great and very well done. There is no substitute for the real thing after all and obviously perfect for your boat in your storage area. This is pretty involved the more you think about it. What about the thermal capacitance of the fuel and how does that effect the temperature of the inner tank walls -that would probably be the first place of condensate. What about the material - would think aluminum more susceptible then fiberglass tanks. Shape of the tank would matter too - determining how much of surface area is insulated, in contact with fuel, in contact with outside air, and internal air. The technology is definitely there to model these things.

Anyway - I filled up for season lay away but sneaking a bunch of rides in til she comes out. Don't think I'm going to worry about filling her again based on your results. Not questioning you, only thinking out loud as a break from the work day and appreciate the thought provoking results.

 

[MikeP]

This article was published several years ago re this subject. It, and my own 30+ years of experience paying no attention at all to whether a winterized vehicle has an empty or full tank and suffering no adverse effects at all, convinces me that it's totally a non-issue. (except for people who would gain by selling you something related to it)

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

 

[smoothmove]

This article was published several years ago re this subject. It, and my own 30+ years of experience paying no attention at all to whether a winterized vehicle has an empty or full tank and suffering no adverse effects at all, convinces me that it's totally a non-issue. (except for people who would gain by selling you something related to it)

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

Now THAT'S what I'm talkin' about. Even if it is by a dead guy ;-)

Thanks for posting that. Pretty good information that you'd think BoatUS would be aware of.
ej

 

[Trojan]

Nice job, very interesting. My boat sat for 2.5 years out of doors. I added 50 gallon of fresh diesel to the 50 gal that was it and fired it up. No water all. It ran fine. I have never had a problem with water in any boat or farm equipment from setting. I think your test proves that condensate in fuel is bunk. Another group of zoomers bite the dust.

BILL

 

[krush]

The liquid and thus tank walls are not going to change temp as much as the ambient air because of the amount of "thermal mass".

 

[sgharford]

Great Thread - I always hated filling the tanks only to put her away for season. I like the idea of less weight having to be supported too.

 

[Boatsb]

Still Ethanol has other issues that make it more important than ever to pay attention.

Phase separation will occur regardless of the amount in the tank. It degrades faster than straight gasoline and will cause problems in the carbs and other fuel system components.

I would empty the tank as much as possible. Pump it out and use it in the cars. Run the carbs dry or feed in some ethanol free 93 octane for the winter.

I had to get in the habit of draining the carbs on the bike because it was gumming everything up between runs if I let it sit more than a month.

 

[MikeP]

Stabil will allegedly handle ethanol in gas with no issues for prolonged storage. They claim a year and I currently store two different cars for from 3-6 months a couple times a year with gas in the tank/stabil with no issues at all and instant starting as soon as I connect the battery/turn the key. So I personally believe their claim - at least as far as 6 months. This winter they will be sitting in the garages for 7 months so I'll see if they can go another month!

I don't fill the tanks, just wait till they are nearly empty, dump 5 OZ of stabil in and add 10 gal of gas - about 1/2 tank in one car, a bit less than that in the other. When I get back to the cars months later I don't fill them with fresh gas, just drive them normally until the gauge shows the usual fill-up point - about 1/8 tank or when the low fuel light comes on.

I see that Stabil now recommends adding it at every fillup to "ensure" no problems with ethanol. This bothers me a bit because it smacks totally of trying to make a buck (a bunch of bucks, actually) from fear. And I hate to see companies that I think make a good product descend to that level but money is money...

 

[SKYCHENEY]

What really irritates me is that companies still market "dry gas" products. Most of these gasline antifreeze compounds are nothing more than straight ethanol or methanol. What do you need that for? You just filled up with E10. Adding another 6 ounces of overpriced alcohol isn't going to accomplish anything.

I have no idea what is in the Stabil product, but I'd like to know what it is and how it works. AFAIK it may just be some more alcohol with some red dye in it. Hopefully I'm wrong and there is at least some benefit to using it.

 

[MikeP]

I BELIEVE that there is no alcohol in Stabil but I don't know that for sure. Totally agree re adding alcohol products to gasoline - makes no sense since the alcohol is already there.

It is interesting that back in the early 70's Norton Motorcycles identified problems with heet/drygas, etc that folks were putting in the fuel to absorb any water caused by condensation. The alcohol was dissolving the resin so a problem that didn't really exist (condensation) was "fixed" by a product that essentially destroyed the tank.

Interestingly, re fuel storage, this is on the MMO FAQ site:

Can I use MMO for winter storage as a fuel stabilizer?
Yes, you can use MMO as a fuel stabilizer. Use 4ozs of Marvel for every 10 gallons of fuel.

http://www.marvelmysteryoil.com/index.php/site/faq/

 

[smoothmove]

Adding STABIL (or one of a host of other products) to keep phase separation from ocurring.

OK, now that's ANOTHER thing I don't necessarily believe. Again, I have a little experimental evidence on my side. I took some ~10% ethanol gasoline last year and added the recommended amount of "Stabilizer" - in this particular case it was a Startron product. I then added 5% water and shook the container. The "stabilzed" gas separated exactly like the unstabilized. Admitedly the 5% figure is probably pretty severe, but it certainly could happen. This is another area that calls for a little basic research. Perhaps, it does work at lower water concentrations, but again, where's BoatUS? Where are the test results?

I use Stabil for other reasons. It's a good product. But if I can quote the Amazing Randi, "Extraordinary claims call for extraordinary evidence."

ej