Storage length for fuel?

It's not impermeable.

Google " Water vapor transmission rate"

Basically water vapour passes through the plastic at a slow rate, which is not a constant but varies according to the humidity difference between the inside and outside of the container, temperature, plastic used, and the fuel used (if it's better at sucking up water then it will increase the inward rate).

It's not much but it's some, and as been pointed out if you have it on concrete or in a garage where the humidity outside the container is higher than inside it will increase. Of course a opened (or broke) deal will alse make this worse.

That said my fuel sits in a sometimes damp garage over the course of a season and I've not seen any ill effects. I buy at shows and use over the next year, and it's fine

Gavin, our jugs are made of polypropylene. They are not a film but about 1/16" thick which is impermeable I cannot find anything in google with a chart of materials but ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) does not even list it. However Polyethelene that is .002 inch's thick has a permeance of .16 gr/Hr ft2 in Hg for a thickness of .01 inches it is a permeance of .03 (I won't bother with the units again). Notice for a thickness of 5 times the permeance goes up 5.33 times. By the time you get to a 1/16" it is almost nothing. Compare it to aluminum foil which is also used as a vapor barrier. For a thickness of .00035 in it has a permeance of .05 but for a thickness of .001 it is a flat 0. We use a thinner amount of polypropylene on milk jugs. You never see the milk evaporating out of the container, do you?

People have mixed up to 20% water into their fuel as an experiment, and seen no ill effects. The engines still ran fine. Maybe not as much power, but they ran, and ran reliably.

There are so many fuel myths out there, it's hard to know what to believe.

"> Gavin,

While I'm not an engineer, Sport Pilot, I am in the plastics industry. Blow molded bottles in any material are not impermeable though the polymer (PP, PE or PET) itself may be. I've seen many instances where the bottle leaks because the "pinch" which seals the tube (parison) is not perfect. In fact, many milk jugs which are sold in markets are very slow "leakers" as a result of this. You may never notice the leak, because you use the milk pretty quickly, but it is there in more cases than you would believe.

At present, I have a one gallon bottle of glow fuel sitting on my shelf which has an extremely slow leak. I noticed it just two weeks ago. The bottom of the bottle was slightly oily, so I wiped it off two weeks ago. I checked it a week ago and found nothing. I checked it yesterday and found the bottom of the bottle to be oily. The seal has never been broken on this bottle of fuel. And comparing it with other bottle of the same brand, there is about 1/2 inch less fuel in this bottle than in others.

Harlan

A fuel leak caused by a very small hole due to an imperfect process is not what we are refering to. We are talking about water transmision through the solid plastic. Most non reactive plastics are impermeable to water when the plastic is thick enough. In any event the fuel or at least the oil was leaking out, water was not getting in.

Water permeating through plastic fuel containers when stored on concrete ????

So highly unlikely as to be deemed not possible.

Water condensing and getting back into the fuel ?????

If we are going to have water condensing inside a partialy full and sealed fuel container then there are only two possibilities.

The very small amount that might be in the air that entered when fuel was removed.... OK I guess we can forget about such a small amount.

The water was already present in the fuel to start with ! In that case I would buy my fuel from a different source !

Anyway it isn't going to happen.

If there is such paranoia about not putting plastic fuel containers on concrete floors and not using fuel that has been stored for lengthy periods then how the hell can some of us use diesel fuel ????

Ok diesel fuel comes in metal cans but it still has a screw on cap. The ether in diesel fuel is highly volatile and will dissapear faster than you can sniff it >:-)

Guys have used 10 year old diesel fuel that has been damn near forgotten about and seen no difference in starting and running. Glow fuel by comparison to diesel is an easy substance to handle and store.

Reg

Any thing getting out will result in a slight (and I'm really talking slight) reduced pressure inside the container, and hence draw the outside atmosphere in.

Given water vapour molucules have a molecular mass of 18.02 and in the worse case castor oil is around 300 (Ok I've no idea what synthetics are used in fuel hence my sticking with castor) if oil can leach out, then water vapour can certainly leach in.

Methanol is known to readily absorb water, why make it easier by leaving fuel in a damp place where temperature and humidity changes may affect it, or make / buy more than you need for a season at most.

I've got a case of Cool power 30% heli fuel that's been sitting for literally 15 years, unopened. Gave my bro-in-law a jug a couple weeks back and he's been flying his heli on it. Zero problems with power or performance.

Not buying the water absorbtion bit....

The water vapor in 60 degrees air and 100% humidity has a presure of only about a half inch of mecury, (.52192 in. Hg to be exact) The pressure of the fuel is 29.92 inches, so the moisture is not going through even if not permeable. If you have a leak the seal of the cap should hold, however air will be sucked back in the hole when atmospheric pressure changes, or when enough fuel leaks to cause the pressure to drop enough to cause the air to schlup back through the hole. Thought the technical term might help explain it. ;>)

Reminds me about the one not to store batteries on cold concrete. But actually if you leave acid in any battery without occasional recharge they will eventually go bad. The trick is to get a large plastic pail, turn the battery upside down, drain the acid in the pail, store the acid in a seperate container. I have heard of replacing the acid with distilled water also, but I am thinking this is another wives tale, I am thinking the water would disolve some of the lead paste, which would then go down the drain when you empty the water.

"The OTHER Kevin in San Diego" wrote in message news: snipped-for-privacy@4ax.com...

It truly depends upon the condition of the container.

I bought a case of Sig 5% nitro all castor lube for some old engines that I run occasionally. Two of the bottles began leaking contents onto the floor after a year or so. Wipe the bottoms off, no drops form while you are watching, but come back later and you have oil (probably really fuel). Must be a pinhole there somewhere.

The fuel is fantastic fuel, so I'm not criticizing Sig's product. Stuff happens and I imagine that these two jugs are defective in some manner. Oddly enough, they are not quite down to being half empty. Strange. the leakage appears to have mitigated somewhat during the last year. I had them outside along side of the shed after spotting the leaks. Was going to use them as weedkiller along the fence. I decided to run some of the stuff just to see how it runs. It can't hurt anything, so why not?

Ed Cregger