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Are you being short changed on glow fuel?

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Are you being short changed on glow fuel?

Old 09-19-2014, 12:54 PM
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Default Are you being short changed on glow fuel?

I think that a well known fuel manufacturer is shorting us on fuel. I discovered the problem when I had the occasion to measure out fuel while mixing a special blend for 1/2A engines.

I have a fresh gallon of fuel I suspect is short, it's 15% nitro and 18% oil and it weighs 7.6 lbs with container. I think it should weigh just over 8 lbs including the container. I recently weighed an empty fuel container at 12.8 ounces or about .8 lbs. So I have a net weight of fuel of 6.8 lbs in this particular container. Is it short?

I need to buy more fuel from my local hobby shop (Dallas) but I don't want to get short changed again, so this time I'm taking my scale.

So here is the question:

How much should a gallon of fuel weigh with and without container?
How much does YOUR fresh gallon of fuel weigh?
How much do other containers weigh?

Last edited by 049flyer; 09-19-2014 at 01:02 PM.
Old 09-20-2014, 02:52 AM
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Well, the components that fuel companies vary by weight day to day and by temperature. I don't have numbers for mixed gallon weights handy but here's some data you can extrapolate and get a pretty good idea of what a gallon should weigh.

Nitromethane is about 1.15g/mL
Castor oil is .97 g/mL
Klotz Techniplate is .91 g/mL
Methanol is .79 g/mL

Other synthetics have different weights, but Klotz is what I have on hand and what I sometimes use. I mix my own fuel exclusively.
Hypothetically, a gallon of 15% nitro 20% oil (50/50 oil blend to be easy) and 65% methanol would be as follows.

I convert to metric because its a bit easier IMO. 1 gallon (128 fl oz) equals 3,785mL. By volume; 15% nitro is 567.75mL @ 1.15g/mL is 652.9g. 10% Klotz oil is 378.5mL @ .91g/mL is 344g. Castor is 378.5mL @ .97g/mL is 367g. Methanol is 2460mL @ .79g/mL is 1943.6g. Total is 3308g or 7lb 4.7oz minus container. This is an approximate number, I truncated some decimal places for ease. I am pretty sure my math is good but don't quote me 100% on it, it's early still . An 80/20 castor/synthetic oil blend would weigh approximately 3293g or 7lb 4.1oz. An 80/20 cas/syn blend at 18% oil is approximately 7lb 2oz. My typical fuel blend is 5% nitro 20% castor which has a net weight of 6lb 15.7oz.

Even my rough math shows my net weighting a finished gallon minus jug to be about 4.5% heavier than what your gallon weighed. You're probably getting short changed on nitro, but some companies cheap out on oil too. It's hard to say without having a lab test a sample.

AHH!! Too much math for 5:30 in the morning Hope this helps you some even if the math is a little off.

Last edited by 1QwkSport2.5r; 09-20-2014 at 02:57 AM.
Old 09-21-2014, 11:56 AM
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Weight of empty plastic 1gallon jug - 4.8 0z
Weight of empty metal 1 gallon jug - 12.8 oz
Old 11-06-2014, 07:29 AM
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I went through this fuel mixing subject some years ago and found that a "well known" fuel blender mixed by weight while the majority mixed by volume. There is a notable reduction in nitro when you mix by weight. It's quite possible that you got the mixed by weight variety.
Old 11-07-2014, 08:38 AM
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Just to confuse things more, Some shippers will only ship Nitro that is mixed 50-50 with methanol. There was a nasty rail fire that changed the rules a number of years ago with Sig fuel being dragged into it. I am sure Sig would allow for the nitro dilution, but others may not be aware of this, or don't care. Nitro is the heaviest part of the fuel, and would make a difference on the higher nitro blends. I have heard some Chinese nitro is not diluted, but you may never know the source. I won't pretend to know how to calculate the specific gravity of all the ingredients, not because I can't, but some smoke may come out of the brain. I would think some different oils may have much different specific gravities than others, castor or synthetic...
Old 11-07-2014, 10:07 AM
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I measure the weight of the nitro and oil when I mix fuel. The density changes with air temperature. I figure out my component volumes by percentage then determine the weight of that volume and use a scale to mix the fuel. If you know what kind/brand of oil the fuel company uses, you can determine what the real percentage is through weight.
Old 11-09-2014, 08:11 AM
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I have noticed that the bottles are not always filled to the same level. I suspect this is caused by leaking or evaporation due to a bad seal, but I suppose it could just be poor quality control of the filling process.

The thought that the manufacturer could be shorting us on the nitro or oil never occurred to me. I hope that is not true. That would be pretty low.

Last edited by JPMacG; 11-09-2014 at 11:03 AM.
Old 11-30-2014, 07:08 AM
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Take a scale to the hobby shop and see what the difference is. You might be surprised.

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