I actually did test the Water Wetter stuff about 10 years ago, when I still had a 4-row radiator factory style radiator (went to aluminum a long time ago). I too suffered from "heat creep", and it would go to 200 degrees, then after driving for awhile, sitting in traffic it would go to 205. Then sitting longer it would creep to 210, then 215.

I bought 2 bottles of Water Wetter, and let the car idle in the garage for about 20 minutes. Same conditions I've always had, all I did was add the Water Wetter. The stuff actually worked. Temps never went above 205.

The down side was that I used to swap intakes a lot, and didn't have the intake crossover cut. That meant I had to drain fluid to get the intake off. I'd reuse the fluid if I could, but I realized that special fluid was not the answer, and that it would get expensive with all the intake swaps I did. But the stuff actually worked.

Went to an aluminum radiator, full vac advance on the timing, always stayed with the factory clutch fan, and the car runs at 190 all day now. I had an electric in front of the radiator, but later removed it. It worked great at the dragstrip, in between runs, to cool the engine down. But I don't race the car anymore, so I removed it.