I agree with the exaggeration statement. The anti-Ethanol factions take partial facts and twist them into apparent truths.
The water Myth...
A half filled 20-gallon tank of ethanol fuel represent a considerable thermal mass.
It will remain warmer than the surrounding air.
The evaporating fuel will tend to push vapors out of the fuel tank preventing air infusion into the tank.
Minimal air will diffuse into the tank.
Gasoline vapors are heavier than air, so the air will tend to float on top of the fuel vapors and be the first gas to get pushed out of the vent during the warming cycle.
The vapor filled upper areas on the inside of the tank may promote water condensation (Sweat!) on the Outside of the tank but not on the inside.
Let's consider a worse case temperature fluctuation.
Assuming a 20-gallon tank half filled with 10 gallons of fuel, and 10 gallons of vapor.
In order to get the tank to breath 1 gallon worth of air each day the temperature would need to vary by 10% cyclically. 10% of the 10 gallons.
That 10% is in absolute values. Room temperature is about 300°K (27°C) (80°F)
A 10% change would be 30°K (30°C) (54°F)
This would mean the temperature swing of the tank and fuel would need to be more than 30°C/54°F to move 1 gallon worth of humid air into and out of the tank every day.
30°C/54°F is an unreasonable amount of temperature swing to occur on a daily basis anywhere in the world. But let us assume it could happen.
Remembering from post #10 that 20 gallons of fuel would need to condense all the water out of 5400 gallons of 50% humidity air to become saturated.
This means we will need to condense out every drop of the water from 2700 gallons of our 50% humidity air to saturate our 10 gallons of fuel in the tank.
At 1 gallon per day, it will take 2700 days (7.4 years) of perfect conditions every day to start phase separation. 80° days, 26° Nights!
If we hangared the plane in a 100% humidity sauna and cycled the temperature daily, we could do it in under 4 years.
I have ongoing experiments myth-busting Ethanol.
I have a liter jar initially filled with 800cc of E-10 auto gas.
It has a short vent tube simulating a fuel tank vent attached through the lid.
It has been sitting on a shelf in an unheated detached garage since 2012.
After 6 winters and summers, 28% of the fuel has evaporated. The lid is showing some rust.
The fuel is noticeable brownish and smells a bit like turpentine.
The one thing that is not showing is any water.
Not a hint of cloudiness. No phase separation. No Water.
The Fuel is Old and Varnished but it is not waterlogged.
Another jar, only 10% full, has evaporated 50% of its initial fuel.
It also shows no water.
If you have water in your tank, it came in as liquid water, Not Vapor.
The Phase separation Myth...
10 gallons of E-10 fuel contains about 1 gallon of Ethanol.
10 gallons will support about 6.4 ounces of water in suspension.
If you were to add an additional 2 ounces of water you would get the 2 ounces of water at the bottom of the tank along with a few ounces of ethanol.
You would not have all 8 ounces of water and the entire gallon os of alcohol phase separate like an avalanche.
And contrary to popular thinking, phase separation is not an irreversible process.
Adding another 5 gallons of fresh fuel to the tank would cause all the phase separated Water/Ethanol to go back into suspension.
This is easily demonstrated at home with a jar of fuel and some water.
Take half a jar of gas.
Drip in water, stirring as you go.
Once it turns cloudy and phase separates...
Add some more gas to the jar...
Clear gas again!
Worried about phase separation?
Top off your tank with fresh gasoline just before the flight.
Water in your tank from rain or condensation is the same issues whether you use E10 or E0.
It is still water in the fuel.
With E0 you will have water you need to drain.
With E10 you will never see it unless it is excessive.