I worked with several PhD chemists who designed coolants for a major oil company. Although CWPASADENA is correct that WW is essentially a surfactant that breaks down the surface tension of the water allowing the water to "touch" the tiny nooks and crevices that otherwise might go without coolant because of surface tension, they didn't think it could be significantly effective because of the large heat-rejecting area already available and doing its job. I suppose the rougher the casting, the better it would work. But the difference between the cooling rates of water/antifreeze versus water/antifreeze/water wetter would be small, if any when compared to the cooling rate already designed into the system. Bassman's comment, I believe, pertains to heavy-duty diesel engines, but I'm not convinced a Model A could generate enough power to make enough heat to boil the coolant on the jacket side of the cylinder, at least not to the point of damage. I've seen displays of erroded diesel cylinder liners that had holes in them on the thrust side from boiling and subsequent cavitation at the cylinder wall. Not a pretty sight, and a very expensive fix. In those cases, because of the mechanism of failure, Water Wetter probably would have had no effect anyway. But if you think it helps and you like it, then use it. $0.02.