[Formulajones]

Originally Posted by track73

Thermostats start to open at their stated temp and open all the way 20 degrees later.

Actually, not to be nit picky, but interesting none the less and fitting for this discussion, from my testing, I've found that stats actually start to crack open roughly about 5 degrees before their rated temp. Pretty easy to experiment on the stove top with a temp probe.

Then when put in service, if you have an excellent cooling system, you can actually see and maintain that crack open temp.

For instance my chevelle has an excellent cooling system, Griffiin rad etc... and the 160 stat in that car actually cracks open at 155, and is fully open around 165. However, as soon as that stat cracks open, on cooler days of 80 or less, it will maintain 155 degrees and is rock steady. Higher rpm on the highway can make the temp rise to 165 but as soon as I slow down it will pull the engine back to 155. Never any colder than that. So most of the time cruising around, this thermostat never even really opens completely, but it does make the engine run at a minimum of 155, and with a good cooling system, the thermostat just barely cracking open is enough to keep the engine at that temp, and will open more if the temp rises. It's doing what it's supposed to do. It's pretty interesting how this stuff acts with a good cooling system.