Which thermostat?

[Bruce Parker (RIP)]

I've run with and without. In warm weather I can't tell the difference (I don't run it in the cold very often). Right now I have a pair of 165 degree ones, just because, as you say, they were there for a reason. One thing I always do is cook new thermostats on the stove to make sure they open before I install them. Some new old stock ones don't open.