Plastic tank?
Drain it. Don't take the chance. I don't care what kind of pure gas you can find. The only reason to keep gas in a tank during storage is with an unlined steel tank to prevent rust.
Pure gasoline still absorbs water and a plastic tank will wick that out of the mix.
I have many friends in Italy, who do leave NCPG (Not Corn Poisoned Gas
) in their plastic tank Ducatis during the winter, w/out any problem.