I recall a similar technical problem dealing with cooling at sub-zero temps and part of the solution was an additive like water-wetter (IIRC) in ethylene glycol. https://www.redlineoil.com/waterwetter
There are a variety of additives available for coolant. Maybe consider a two component solution to your problem? Just be certain it won't corrode or degrade anything in the loop. Ethanol is nasty nasty stuff notorious for degrading containers and will turn some plastics to mush in short order. Of course everclear is quite good in fruit punch. Haha.
Oh pook no... friends don't let friends drive modern GM products..