There are many other cases outside of auto mechanics where too cool of water on hot metal can cause warping and or cracking. As far as the cooling system on a car, the drilled tstat in the summer does lessen the temp changes. I can tell a big difference between my 180 drilled and non drilled 180, fan settings being the same. Does it really matter? I have no idea. If we have a really hot summer, I'll likely put the drilled in until late fall.