[Schulisco]

Originally Posted by safe

Air isn't circulating the tank when stationary over the winter. If you store the car relatively warm and at a constant temperature there will be no water or rusting.

Ethanol doesn't magically make water, if there is water in the fuel system the ethanol will absorb it and purge it when you run.
Without the ethanol the water will "pool" at the bottom of the tank and rust it.
In cold climates we used to add ethanol in the winter to remove water.

No ethanol does not deteriorate gasoline. Gasoline looses its "flammability" over time, that's why I keep the level low so I can fuel up in the spring, but 6 months is really nothing to worry about.

Pretty confident that pouring 60 liters of fuel, with some force like at a gas station, into 20 liters will mix it pretty good. Non issue.

Only few people have the opportunity to store their cars in constant warm and dry ambient temperatures.

I also didn't wrote anything about ethanol is making water. It detoriates and attracts the water, e.g. from the tank ventilation and from the air what's already inside the tank.

Anybody is free to do what he wants to do. But: Recent experience showed that storing the car with a full tank together mixed up with a fuel storage is the best way to store it a longer time. The longer, the more important. Storing the car for les than three months or so you can waive this.

See this three parted article series in a german classic cars magazine due to the introduction of E10 (Gas with 10% ethanol) in Germany back in 2011.
https://www.oldtimer-markt.de/ratgeber/grundlagen/oldtimer-und-e10-%E2%80%93-die-fakten
At the bottom of the article page there are the links to three parts of the article as PDF files, I let Google only translate the 2nd part. The pictures are self explaining. Mostly on carburettors, but also the aluminium and steels parts of the CIS would be affected in the same way.
https://uploadnow.io/f/S4rjby8

Thomas