I can't imagine ethanol being a good idea. E85 eating rubber gaskets and seals in older cars not designed for it is apparently an issue (though I've ran E85 in my old non-flex fuel Silverado for months just fine without ill effect, just going off what the mob mentality seems to suggest) and I can't imagine it being any better in a loop.
Propylene/ethylene glycol would be my bet. Most of the temp ranges are off specific mixtures, usually 30/70 or 50/50. Get the non-premix and mix it yourself to the temp range you need and no slush.