[JFMetter]

This is interesting. I started a thread over in Heating and Cooling TECH (Getting the Therm Housing off a 389 Tri-Power) that ended up talking about t-stats, with ZeGermanHam advising me that t-stats are not magic bullets with regard to cooling a motor. Since I was upgrading a broken water pump with a FlowKooler pump that's supposed to help cool off the motor (with increased coolant pressure and flow) and AMEs suggests using a 180 t-stat with this pump and I had a 195 in the motor, I got to thinking about t-stats. A 195 t-stat will keep the motor at 195 or above. 195 is the lower limit on how cool your cooling system can make the motor run at. Even if the system has the capability of driving down the motor temp to let's say 185, you'll never see that on the motor with a 195. A 195 is closing as the operating temp drops below 195 so the temp will start raising back up till it opens the t-stat at 195 (and back and forth). So if you're happy with your motor cooling, even with the air on, then going to 180 might be just fixing something that's not broken. But it sounds like you're a bit concerned about engine cooling? Asking what temp the temp idiot light trips (by the way, get yourself a laser temperature thermometer - $20 bucks or so all over the place, Amazon..., and you can get the real temperature right off the running engine block, say at the temperature sensing plug area)? If that's the case the t-stat can't help you. You can even pull it and it will not help out. You need to do something else to affect cooling - a shroud if you don't have one (and sealing the edges to create more of a vacuum air flow), or a different radiator, or more ify things like a more efficient water pump/fan clutch/coolant liquids. Then if you do that and want to see this change drive the cooling below 195, a 180 t-stat makes sense.

[jamesn]

I worked at the Stant thermostat manufacturing facility for nearly twenty years. That doesn’t make me a thermostat expert, but I’ve been involved with them more than most people. I no longer work for them so this is in no way an endorsement for their products.
Regarding the Stant Super Stat vs the standard line, the Super Stat is generally better. The return spring is bigger, the heat motor is bigger, the sheet metal is bigger and it has stricter performance and manufacturing requirements.
As usual, bigger is better.

[455'73inElCamino]

I run a 180 thermostat but planning on going to 195. Reason, it takes a fair amount of time for my engine to heat up, and if I am going downhill my engine will cool down to 160 degrees or lower! That is too cold. Engines are design to run hotter.

Carnot engines by design run more efficiently hot (as long as your oil/lubricants to break down) with cold air into the engine. Will get most efficiency and power that way.