I haven't used that, but I have Red Line's "Water Wetter" in my hot rod. Unfortunately, I can't tell any difference. I have so many cubic inches and ponies under the hood, that with my refusal to make any structural modifications, I'm really having a hard time keeping my beast cool; especially with A/C on during a 100 degree day like today. I have a custom built radiator that is as thick and gives me as many cubic inches of surface area as possible, a custom made shroud, and special built electric fans that pull the equivilant air flow of a 9 ton home A/C unit through the radiator. Still, I'm marginal at best on a really hot day and stuck in traffic.
If anyone has used this and it works, I'd really like to know. The Water Wetter has an interesting chemical design and helps some, but not enough. I'm not going to violate the original structural integrity of my car to make changes, so I'm at the mercy of modern chemistry for a better cooling system.
Just in case you don't know, adding anti-freeze (ethylene glycol) to water in the recommended 50/50 mixture actually reduces the cooling capacity of plain water by nearly 22%. The issue, of course, is to make sure that you don't forget to either drain it, or add anti-freeze in cold weather. Boiling isn't a problem if the correct pressure is maintained within the cooling system. Water Wetter and RO/DI water is the best cooling mixture I've found to date. Let me know if anything works better.