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Gasoline Whitepaper by Gold Eagle


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If you want to know a bit more about automotive gasoline, this is a fantastic read!




Of note related to ethanol:


A gallon of gasoline comprised solely of hydrocarbons can hold only 0.15 teaspoons of water (at 
60°F) before the water will separate. A gasoline blend containing 10v% ethanol would require almost 
4 teaspoons of water before phase separation would occur. Therefore in routine operations, ethanol 
is more likely to suspend moisture and carry it out of the fuel system than hydrocarbon only fuels.


Keep in mind the part about ethanol drawing moisture from the air, so just because ethanol holds more moisture, it doesn't necessarily mean it's better.

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The bottom is the ethanol/water.





To put a note forth: I honestly think that the worry about ethanol phase separation is overblown, but awareness of it is nonetheless a good thing. Your plane would have to sit for a long long time before it gets to look like the above.

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The bottles in the pic have a lot of water for that volume of fuel and if you ever saw that water separate out of our fuel it's time to dump the fuel if it has ethanol. Plain gas could technically still be used because the water isn't adsorbed in plain fuel as it is with ethanol. 

It will take 17 teaspoons which is slightly more than one cup of water to fully contaminate our 17 gals of plain fuel and 4 times that much if it has ethanol. That's so much water that that would never enter through the fuel vent especially since fuel has a vapor pressure and that is exiting out the vent all the time. For that much water to get in there it went in with the fuel. Most traces of water that may get trapped in the ethanol usually just burn through the system.


The hype over ethanol and water in our fuel getting in through a fuel vent is just that, hype. If you pour it in then it would still take a lot to cause any serious issues.


As an example:

How many here using ethanol laced fuel ever find any real water in the gascolator?


If you ever do see water in the gascolator and your using ethanol fuel then it's time to replace the fuel. If water has saturated the fuel that bad and the water falls out of solution with the ethanol it takes fuel additives and octane with it. The fuel usually will drop about 3-4 octane points. These guys that advertise washing fuel  with water is exactly what they are doing. Trapping the ethanol with the water then draining it off. It's not even an efficient way to do it.

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