I helped my son replace the thermostat in his Mustang today, assuming that his 'no heat' problem was typical. We bought a 'stat from Autozone that claimed to be original equipment.
The first thing we did when we got home was drop the "bad" 'stat in a pot of water with the good one, and fire up the stove. They both opened up at about 190-200, but the new one opened up a lot farther.
I'm thinking that's too high...any idea what the temp of the 171ci (2.8) 6-cyl engine is supposd to be?
-John O