Thermostat ratings

[diesel_lv]

I've never put a thermostat in hot water to check one before, never needed to. So yesterday I found about 3 laying around my garage and decided to check them. One 160° Stant, one 180° Stant and one 195° Robert Shaw. Every article I've ever read on cooling says the rated temp is the start opening temp and fully open 15° later. Every one of them started opening 15° cooler and fully open at rated. I kept wondering why my car would never get over 148° in the winter and 157° in summer on the interstate. I had a 160° Robert Shaw high flow. It starts opening at 145°. Changed it to a 195° Robert Shaw for the coming cooler months and will see if I can finally get my car to run at 180-185ish.

 

[64fury74charger]

I've never put a thermostat in hot water to check one before, never needed to. So yesterday I found about 3 laying around my garage and decided to check them. One 160° Stant, one 180° Stant and one 195° Robert Shaw. Every article I've ever read on cooling says the rated temp is the start opening temp and fully open 15° later. Every one of them started opening 15° cooler and fully open at rated. I kept wondering why my car would never get over 148° in the winter and 157° in summer on the interstate. I had a 160° Robert Shaw high flow. It starts opening at 145°. Changed it to a 195° Robert Shaw for the coming cooler months and will see if I can finally get my car to run at 180-185ish.

I have always tested any thermostat going in one of the cars and then I can be reasonably sure it will work properly. Both cars run 180 thermostat and both cars reach 190 when it first opens then run between 180 and 185 steady. Both have aluminum radiator and mechanical fans. Good known accurate mechanical gauge and thermal temp gun also.

 

[Geoff 2]

My experience. Stant stats are bang-on the rating.
A 160 stat should open at 160 & take another 20-30 to fully opem.
Robert Shaw, Milodon, Mr. Gasket hi-flow stats. All the same, different psackaging. The original US made stats were all brass. The Chinese versions which is all I see these days have a 3 point s/steel upper bridge.
[1] The Chinese ones can jam when new because the seal is tight in the barrel. A little bit of ATF dribbled in usually fixes it & after the first operation are usually reliable.
[2] The Chinese 160s open at 160 but if the engine cools down they can drop to about 130* before they fully close. Unreliable.

 

[Don67Satellite]

I run a Robert Shaw 180 and cruising down the road it is between 180-190 depending if city or highway driving. Mechanical 18" steel 5 blade fan and Flowkooler WP.