Old Fuel and Hydrometers?

[Douglas Ames]

Not sure what forum to post this in so here goes-

I saw this Methanol Hydrometer while surfing the net and wondered if my old gallon of fuel (1/3 left) had any measurable water content. I'm going to try and find one locally now that my curiousity is up,
but is this the right instrument for this?
Is it something to worry about with older fuel sitting about?
Would castor or nitro affect the results?

http://www.tooltopia.com/ez-red-s104.aspx?utm_source=pricegrabber&utm_medium=cse&utm_term=EZRS104&utm_campaign=pricegrabber_r1

[Bob Reeves]

Doubt it would tell you anything useful. Think I remember reading someplace that someone added water to fuel just to see how much it took to make it do something funny and it was at or over 10%. For fuel to absorb that much water it would have to increase in volume, never seen that happen. Run the fuel it will work fine especially for the kind of flying we do.. Might be a different story if trying to break a speed record and everything had to be perfect. 

[Alan Hahn]

I think the problem is that you also have oil and nitromethane in the fuel, so that will confuse the Hydrometer, which basically is just measuring the difference between water and water+ stuff.

I use one when I make homemade beer. Mine is calibrated in sugar equivalents which will ferment down into alcohol.

[john e. holliday]

If your fuel starts acting funny or engine for that matter, think of how the fuel was stored.  If sitting on a concrete floor in plastic jugs it will absorb moisture.  I was told to always put a peice of wood under the jugs no matter where you store the fuel.  If the engine does start acting funny with the fuel, try fresh fuel.  When thing start working right again, use the old fuel for break in on the bench.  I have mixed it half and half with fresh fuel for sport flying with no problem.

[Serge_Krauss]

I often use year-old fuel. It hasn't caused any real problems, although I know it collects water, despite carefully capping the cans at the field immediately after drawing fuel. The big clue is change in NV settings and a perceptable change in RPM when switching to a new can.

SK

[Alan Hahn]

I should note that I store my "fuel" in a plastic bag in the fridge. When I take it out in the springtime, I let it warm up in the bag to avoid condensation.

My fuel is a lipo battery!

[John Cralley]

I have a jug of fuel that is at least 20 years old. Used it last Summer in a Fox 35 stunt and it ran fine. I suggest you just try the fuel and see how it works.

By the way: A hydrometer is an instrument used to measure the specific gravity (or relative density) of liquids; that is, the ratio of the density of the liquid to the density of water  From Wikipedia, the free encyclopedia. I suppose you could calibrate the hydrometer for your fuel by taking a batch of fresh fuel and adding water while using the hydrometer to measure the different specific gravities as various amounts were added.

Lots easier to just try the fuel and see how it works! LOL

[Brian Hampton]

I played around once with adding water to fresh fuel to see what affect it might have (it was with an RC model so nothing valuable ). I started with 2% water, no different to fresh fuel as far as starting, running, flying so I went to 3% on the next tank. Same same, no problem. Next tank was 4% water. Oops, the engine wouldn't even fire let alone start. After I drained the fuel back out into a squeeze bottle I could see that all the oil had fallen out of suspension to the bottom of the bottle which meant that, in the clunk tank, I was trying to start an engine with 100% oil as a fuel. Back at home I did some more playing around and found that tolerance for water is dependent on fuel temperature. The colder it is, the less water it needs before the oil drops out. The type of oil made a difference too with castor being able to handle more water than a synthetic I tried. I don't use nitro so I can't say if that makes any difference.

[Gene O'Keefe]

I've used fuel stored in dark basement on concrete floor in plastic bottles that was 5 to 10 years old with no running
problems whatsoever. I agree with John...run it !

[ugo merlo]

if fuel keeps water, you can dry it in a simple way, keep some moisture adsorber, put in, shake well, wait for it to set and discard the bottom layer.
useful dryers are, calcium chloride, magnesium sulphate, plaster of paris also...all well dried or baked.
ugo

[Douglas Ames]

I think the problem is that you also have oil and nitromethane in the fuel, so that will confuse the Hydrometer, which basically is just measuring the difference between water and water+ stuff.

I use one when I make homemade beer. Mine is calibrated in sugar equivalents which will ferment down into alcohol.

I was wondering that...if the oil would throw it off.
I also used to brew beer over ten years ago. Had a real good batch of Ginger beer once!

[Brett Buck]

Doubt it would tell you anything useful. Think I remember reading someplace that someone added water to fuel just to see how much it took to make it do something funny and it was at or over 10%. For fuel to absorb that much water it would have to increase in volume, never seen that happen. Run the fuel it will work fine especially for the kind of flying we do.. Might be a different story if trying to break a speed record and everything had to be perfect. 

      That was Joe Wagner. I certainly agree that it's just about impossible to absorb that much from the air. But I have run fuel with water intentionally added as a test (way back in the good old days) anything more than about a tablespoon in a gallon had marked effects on the run quality on my Fox.

   I don't worry a lot about picking up water - just be careful and never leave it open for any length of time, and it will be OK. But I am skeptical that a large amount makes no difference.

     Brett

[Bob Reeves]

Ya, I couldn't remember the exact numbers but remember it was allot more than I would have thought. My thinking is we actually have more trouble with evaporation reducing the alcohol and nitro content than absorption but I'm not a chemest so just a guess.