I used to like Robertshaw but I can't figure out where they went.
I replaced the OEM-looking 'stat in my wife's '94 Acclaim with a Stant last year. The temperature went from rock-steady at all times to very, very variable, sometimes approaching overheating when I'd idle in a parking lot after a good drive. Looking at the brand-new Stant in front of me next to the OEM-looking oldie, it's obvious the flow hole in the Stant is considerably smaller.
Went to AutoZone and they sell three no-name brands, all of which looked to me like cheap tin stampings (though they had about the right size of flow hole) so I took a pass.
The rubber bushings (!) in the OEM-looking 'stat are cracked badly, or I'd put it back in.
So who (preferably in meatspace) sells decent auto thermostats?