X - 2Y = X
X is right.
Water Wetter or the like "aides" in the cooling ability of water (not antifreeze mind you!)
However it's effects are minimal and really only "noticed" under heavy heat inducing situations. Like WOT runs or especially "boosted" WOT runs for instance.
It will help the water absorb more heat energy. That is a fact.
However not remotely close to what was stated by Y. Especially at idle or moderate load.
Yes I use water wetter.
