This site maintained by: Curtis L. Olson
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Storing Fuel for Maximum Shelf Life – Part
5 The following is the fifth in
a series of articles exploring all facets of model engine fuel. The writer is Don Nix,founder
and former owner of POWERMASTER FUEL. Readers are invited to
contact Don directly via e-mail – FLYERDON@aol.com During the Q&A part of countless
“Dog & Pony Shows ” at hobby clubs all over the U.S., one of the frequently
asked questions is, “What ’s the shelf life of fuel?” The answer is both simple
and easy. Properly stored, model engine fuel will last almost indefinitely. So,
what constitutes “properly stored ”?Let ’s take a look. Contrary to many things you might
have read or heard, just about the only thing that adversely affects model fuel
is the absorption of moisture from the air. Keep the air away from it, and your
fuel will likely be potent longer than you are! Methanol -the major ingredient
in model fuel- is hygroscopic. This means it’s virtually 100% soluble in water,
and absorbs moisture from the air like a vacuum cleaner sucking up dirt. Most modelers have no idea how
rapidly this can and does happen, and tend to be rather skeptical about the
idea. Let me paint a picture for you. Almost everyone has spilled a little fuel
on the top of their fuel can in their flight box. If so, you’ve no doubt
noticed that the shallow film of raw fuel takes on a cloudy, milky look. What
you are seeing is the methanol sucking moisture right out of the air. Since the
quantity of fuel is thin with a lot of surface area, the absorption is rapid.
The water won’t mix with the oil and the fuel turns cloudy. Just remember how
quickly this happens, almost immediately, and it might give you an idea of just
how quickly your fuel can be ruined if you leave the cap off, allow a vent tube
to remain open, etc. The wide surface area relative to
the quantity of the fuel exposed is disproportionate, of course, to leaving the
cap off the fuel jug, but I think you get the idea. In a humid conditions such
as exist in parts of the U.S., it doesn’t take very long at all to adversely
affect your fuel. And it doesn’t take a large opening, a crossthreaded cap, a
small vent line, etc. is all that ’s needed to do the damage. The solution is simple, of course,
just keep it tightly sealed. And yet, sometimes that ’s not enough. Most of us
have seen small droplets condensed inside our fuel jugs after it ’s become
partially empty. This is the result of condensation of moisture as the air
trapped inside the jug cools. Until about a year ago, there was little we could
do about this, but there is now a method to take care of this problem. Since it
’s not the purpose of this column to commercially promote our own products,
those interested are invited to contact the writer at the e-mail address above,
and we’ll be happy to tell you about the product that will solve the problem. For the reasons above, it ’s our
opinion that it is rarely a good idea to buy model fuel in 55-gallon drums.
Unless all the fuel is poured up the first time the drum is opened, a
substantial volume of air is trapped inside the drum each time it’s opened.
Steel containers of any kind warm and cool much more readily and rapidly than
plastic containers and condensation is much more evident in this type of
container. The result is that the last portion of the drum of fuel is quite
likely to be contaminated with moisture, sometimes to the point of being
unusable. There is another downside to buying
fuel in drums, especially if more than one person is using it. With no control
over the type container the fuel is dispensed into, perhaps not bearing
sufficient or proper warnings, etc., the liability is incredibly high if an
accident of any sort should occur. Model clubs considering this type of fuel
purchase for their members should be particularly aware of the potential liability,
which is huge! While it ’s true that the UV in
sunlight (or in fluorescent lights, for that matter)will cause pure
nitromethane to deteriorate over time, it ’s our experience that once the nitro
is in solution and substantially diluted, the deteriorative effect is
relatively minor. To test this, some years ago we put
a gallon of 10% fuel out in direct sunlight (in sunny Southern California) for
a month. At the end of that time, we tested that fuel in an engine vs. fresh
product and could see no difference. While it certainly won ’t hurt anything to
store fuel away from direct sunlight, etc., it ’s our personal opinion that the
adverse effect of sunlight on fuel under normal operating conditions is too
little to worry about. |