[bluGill]

> In concentrations used as a fuel (e.g., E85), it acts like a desiccant and spoils quickly

Citation needed. (hint you won't find one because it isn't true). Be careful here - this myth has been repeated enough that a search will find plenty of claims that don't check out.

High concentration alcohol doesn't spoil. Even lower concentrations don't spoil, but they mix with poor quality gas that does spoil. Well when you get very low it will, but alcohol is poison to living things and so it won't spoil. (I'm not sure how ethanol stands up to UV - but we generally keep it in a tank so that isn't an issue)

Ethanol will absorb water, but it doesn't take it out of the air anymore than anything else.

[red-iron-pine]

nah, it loves to absorb water out of the ambient air.

ethanol that is distilled forms an azeotrope has a hard time getting past 98% on its own. even if you used advanced techniques and additives, it has a strongly hygroscopic nature, meaning it actively attracts and absorbs water vapor directly from the air.

in other words, it will do everything it can to get back to 98%.

to keep ethanol above 98%, you need airtight seals or "molecular sieves" (zeolite beads) inside the tank to constantly "bead up" and trap any incoming water molecules.