I installed a Mopar 195° T-Stat about half a year ago after having issues with a Stant Super 195° dropping down in temperature to about 160° when cruising down long hills off-throttle.

My normal operating temperature as shown on the factory gauge is about 182°F, halfway in between the 210 mark and the mark to the left.

I used a Fluke IR gun to check the temp of the t-stat housing and I got values from as low as 183 up to 201° depending on where I was pointing at. I'm going to try and borrow a Fluke camera from work to get a better idea of the temperature.

If I am driving up a long hill however, at about 3,000RPM for a few minutes the temperature will stabilize right at 210°F and remain there. This is where I would prefer to run for reasons of engine wear and fuel economy.

Should I switch to a 205° thermostat due to the Northern climate here, or do I have a bad Mopar thermostat?

 

I don't think you have a problem. I'd leave the t-stat alone.
The dash gauge I wouldn't guess as being better than 10%, that's +/- 20 degrees at operating temp. 183-201 at the t-stat is exactly where you should be.

 

I agree I would keep that one.

 

What's your outside temp ? When 30f or below mine will stay below 195, not 160 though. It usually will stay above 195 when under throttle though. Coasting downhill on a cold day I think your normal, if that's the case.

 

Outside temp has been around 35-59°F. This is the ambient temperature when I am running about 180-200°F coolant temperature.

On the mountain passes where I'm giving more throttle the ambient temperature is cooler, down to 5 or 15°F but the coolant temperature remains at a consistent 210°F.

I was under the impression that it's typically normal for an engine to run about 210° with the Mopar thermostat all year around.

 

I recently went with a 195 deg. Superstat and have the same results. one thing i noticed, the PO had a LOT of sealant covering the bypass area of the coolant temperature sensor in the thermostat housing.

After taking IR readings of all the vital areas of the cooling system as it warmed and reached temp as well as after continued abuse (long, slow ascents) I have no qualms about the function of the cooling system.

Theses were my individual results on a commonly debated subject so take it with a grain of salt. hope this helps.

 

Sounds like the consensus is that the temperatures I'm seeing is OK? Won't affect my fuel mileage?

 

This is exactly where you want to be:
182 on the gauge is just fine. I'd worry if you were staying 160-170, I forget the exact temperature the PCM considers "operating temp"....I think it's in there somewhere.

 

Very good, thanks for your help Radi and others.