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Author Topic: Checking oil content of fuel  (Read 1153 times)

Online Larry Renger

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Checking oil content of fuel
« on: July 09, 2009, 11:59:11 PM »
In a past thread, someone suggested measuring out a small quantity of fuel and letting the Methanol and Nitro evaporate to measure the remaining oil content.  I tried that, and the dang stuff just sits there for days with no reduction in volume.  I am reluctant to heat it to hasten the process.  Has anybody else had success/failure in attempting this?

The reason for this is to find out how much oil is in some 30% Nitro car fuel, the only high Nitro stuff I can find.
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Offline john e. holliday

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Re: Checking oil content of fuel
« Reply #1 on: July 10, 2009, 09:30:58 AM »
Use your hot air gun to heat it.  Suggest doing it outdoors tho.  DOC Holliday
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Offline Pinecone

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Re: Checking oil content of fuel
« Reply #2 on: July 10, 2009, 11:22:30 AM »
Having recently done this.  The methanol will boil off first, and if you use a graduated cylinder, it can shotgun the fuel when the methanol boils.  Guess how I learned this. :)

So use a wide, shallow container to get the methanol and some of the nitro out.  Then put back into graduated cylinder and keep warm until the volume doesn't change.
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Offline Wayne Collier

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Re: Checking oil content of fuel
« Reply #3 on: July 10, 2009, 07:28:45 PM »
Hey Pinecone, knowing you're occupation ... If I remember correctly from another thread ... You tried this?

                          just kidding


Wouldn't weighing a known volume of fuel give some indication of contents?
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Offline Bill Adair

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Re: Checking oil content of fuel
« Reply #4 on: July 10, 2009, 07:34:56 PM »
Larry,

I evaporated some samples, but may have left them longer than overnight, and possibly as long as a week. That was many years ago, when I was working long hours, and many weekends. The days just seemed to run together after a while.  HB~>

I've also had good results by burning the samples with Castor content. Tried burning some mostly synthetic oil fuels, but the samples flared up, and splattered burning fuel outside the containers! I'm not sure what caused that, but thought at the time that the synthetic oil had ignited.

The muffin tin that I used, was just about ideal for the evaporation testing method, exposing a lot of surface to the atmosphere.
 
Bill

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Offline Pinecone

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Re: Checking oil content of fuel
« Reply #5 on: July 14, 2009, 01:48:56 PM »
Quote from: Wayne Collier on July 10, 2009, 07:28:45 PM
Hey Pinecone, knowing you're occupation ... If I remember correctly from another thread ... You tried this?

                          just kidding

Wouldn't weighing a known volume of fuel give some indication of contents?

Of course, the standard disclaimer of don't try this at home, I am a trained professional.... :)

You, because of the mixture, it would be hard to figure out the % of three different materials.  Not impossible, but too many variables.  If you had 0% nitro fuel, it would be doable.
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Offline Pinecone

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Re: Checking oil content of fuel
« Reply #6 on: July 14, 2009, 01:52:17 PM »
Quote from: Bill Adair on July 10, 2009, 07:34:56 PM
The muffin tin that I used, was just about ideal for the evaporation testing method, exposing a lot of surface to the atmosphere.

From my testing, without heating, it will be difficult to get all the nitro out.  The boiling point is 100 - 103C.  And the vapor pressure at 27.5C is only 40mm Hg.

But you are right, large surface area is good.  And if heating allows boling without launching the contents. :)

I ended up using a small metal cup that I picked up for mixing paint.  I think they are used for condiments.  I found a 4 pack at Target for about $1.
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Offline Mike Anderson

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Re: Checking oil content of fuel
« Reply #7 on: July 15, 2009, 07:07:14 AM »
Quote from: Pinecone on July 14, 2009, 01:48:56 PM
because of the mixture, it would be hard to figure out the % of three different materials.  Not impossible, but too many variables.  If you had 0% nitro fuel, it would be doable.

What if you assume the stated Nitro %age, and try calculate what's left based on that assumption?  Also, do you have to know the specific oil or are all of them fairly close in density?

One other note:  I sometimes use an old gallon of fuel (VERY old) as a cleaning solution in an ultrasonic cleaner - I do notice that if allowed to sit after using it, the cleaning solution (fuel) seems to reduce to the oil fairly quickly -- like a couple of days.  If I just allow of small amount of fuel to sit in a jar, it seems as though it is a couple of weeks at least and still more like fuel than oil.  Maybe a small ultrasonic cleaner would hasten the evaporation more safely than heating it.
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Offline Pinecone

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Re: Checking oil content of fuel
« Reply #8 on: July 15, 2009, 11:47:18 AM »
But if you are trying to figure out if that fuel company blends to a weight percentage, their nitro content would also be off.

And yes, different oils have different densities.

The methanol evaporates very quickly.  Nitro less quickly.  Large surface area, with lower sidewalls, makes thing evaporate quicker.
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Offline George

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Re: Checking oil content of fuel
« Reply #9 on: July 15, 2009, 12:27:44 PM »
Much safer and easier to buy fuel you trust.  H^^

George
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Offline Mike Anderson

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Re: Checking oil content of fuel
« Reply #10 on: July 15, 2009, 09:25:13 PM »
Quote from: George Bain on July 15, 2009, 12:27:44 PM
Much safer and easier to buy fuel you trust.  H^^

George

Well safer but not necessarily easier - Larry's original post was in reference to some
"car fuel" - the only high nitro stuff he could find.  Around here, Sig fuel is the
standard for us, and the LHS always has a pretty good supply, but the last couple
of months he has been back-ordered by Sig - so that leaves us with the various
RC Kool-Ade flavors until Sig starts shipping again.

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Offline Pinecone

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Re: Checking oil content of fuel
« Reply #11 on: July 17, 2009, 01:47:15 PM »
Quote from: George Bain on July 15, 2009, 12:27:44 PM
Much safer and easier to buy fuel you trust.  H^^

George

True, but I was trying to prove or disprove some statements made by people, such as in this thread, about certain fuels not being accurately reported as to oil content my volume. :)
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Offline Jim Thomerson

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Re: Checking oil content of fuel
« Reply #12 on: July 19, 2009, 07:59:35 PM »
If you add enough water to fuel, the oil should come out of solution and be easily measured.

I'm very sceptical about fuel absorbing water from the atmosphere.  I think what happens with exposed fuel is that the methanol evaporates.  In one of your open fuel experiments, it would be instructional to do it on a scale and see what happens to the weight. If the fuel absorbs water, the weight should go up.  If methanol is evaporating, the weight should go down. 
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Offline Pinecone

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Re: Checking oil content of fuel
« Reply #13 on: July 20, 2009, 12:18:24 PM »
But what about the nitro? :)

Methanol WILL absorb water out of the air.  Methanol will also evaporate pretty quickly if left open with a reasonable surface area.   In a can/jub, I would suspect taht at room temp, it would absorb water.  In teh sun at teh field or in a pail, it would evaporate more.
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Terry Carraway
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