[FrankieT/A]

Originally Posted by Formulajones

Correct, a thermostats purpose is to not let the engine run cooler than the rated temp. It can run hotter, but won't run cooler.

Sounds like your stat may be slightly stuck open, which would also explain why it takes your engine a fair amount of time to warm up. Because it already has coolant circulating even when cold.

Not necessarily true. I have FI on my car and one of the breakpoints for engine temp is 170. My car had a 160 thermostat in it from the carb days. My temp would only get to about 156 or 157. Then I brought the car to North Carolina last week and warmest it would get was 152 (40 degrees outside). I was trying to tune the FI and figured I'm never going to get this right unless I get the temp where it needs to be. So, I changed the thermostat while up there to a 180 Stant superstat. Now my car only gets to about 172-174 which I'm good with because it brings me over the 170 breakpoint I was looking for. Point is my car still does not get to thermostat temp even back in S Florida. Both thermostats did the same exact thing and one was about 5 years old and one brand new. In theory it should bring the temp to thermostat temp. I do have a Flow Cooler wp with about a .010 gap, an aluminum radiator, fan clutch and aluminum heads. My temp guage is confirmed by the FI coolant temp sensor.

And let's not forget thermostats don't open and close...they modulate.