[ZeGermanHam]

I always recommend double-checking the t-stat in boiling water with a thermometer before installing. I bought the "heavy duty" 180F t-stat from Ames a few years ago. Put maybe 20 miles on it before I tore the car apart for restoration. When putting my engine back together, I had the foresight to check the t-stat before reinstalling, and to my surprise it didn't open even when submerged in fully boiling water (212F). I ended up buying a Murray Ultra 180F t-stat from O'Reilly Auto and it opened pretty much right at 180F when tested and has kept my engine dead-on 180F in the summer when temps are in the 70s and 80s, and also recently when driving in 40F temps.

In short, t-stats aren't always what they advertise. Some open too soon, others open too late. Unfortunately, it's on the user to verify function.