It’s been close to a month since I’ve been back to this thread. A lot has happened since then.

1. The coldest it got when i’ve used this mix has been about 17 degrees F.

2. I believe there are different grades of glycerine and glycol. Medical grade will be better (or different) than automotive use grades. On top of that, Ethylene glycol is slightly different than propylene glycol. Ethylene is a 2-carbon based chain while propylene is a 3-carbon based chain. Simply buying something called glycol doesn’t tell you what it is and the concentration application is left up to you. Years ago, I bought a pint of glycerine, mixed it 60/40 with water and put it into the freezer. Two days later it was syrupy but didn’t freeze. Antifreeze glycols will go much lower than that when mixed 50/50. Bob Jameson, Scott Phillips and some of the others on here should be able to give you better information.

I’m not sure if it is necessary, but I mix it with creek water.