There's a product called Water Wetter that changes the surface tension of the water and that improves the contact with the metal. I live where it's 107F today and I can't say that I can prove there's a problem.
I did have a coolant leak and replaced the O ring at the thermostat, that seems to have ended the leak so far. I don't know what caused it to leak, but I was riding aggressive in the heat and it never leaked before. I've put 10,000 miles just this season alone and she's at about 40,000 now. I also have an oil leak that I have to chase down.
I really don't know if it was heat that cased these leaks, but it happened after being aggressive in the heat and she's never had a leak before.
I'd be concerned any mix that may not play well with the rest of the mix. So I'd check if there's any issues there.
What exactly is their claim? They say "up to 30 deg..." I don't like those kinds of claims, I'd like to know what exactly it does.
BeCool has some additives, I don't remember all the details, but it was tested and seemed to help.