Water Wetter does NOT work based on empirical testing. It is a pure surficant (just like soap) and in theory should reduce the surface tension between the block and the coolant, however it does not reduce cooling system temperatures if added to a 50/50 mix. I have 10 runs on a NIST traceable dyno that indicate that the temperature of the upper and lower hose, engine block, and head did not change.
Adding Watter Wetter to pure water may have a different effect, however pure water has about 8% more heat transfer capability than a 50/50 mix, so the claims may be inflated as well.
Just my observations
Scott.