I put Grey 180f thermostat in my 03 D2 last week and see pretty much those same after temps now. My before normal driving temp was 194f.

My cooling system had about 30K miles on it along with a Turner 4.6 engine. Started to fluctuate temps and climbed really high once and noticed the plastic t bleeder failed. Was misting coolant and I would guess sucking in air when off and cooling down. Replaced it with a metal T but still had some temperature fluctuations. Took the thermostat out and it was failing internally. Could see a loose black o ring in it and it was a bit loose inside. The 180f one brought the temps down and doesn't fluctuate as much.

 

Follow up:

I tried the "topping off" method for a week. Each night, park on a hill, nose up. Each morning, open bleed screw and add coolant.

Results: No difference at all. No matter what, every morning there was air in the upper hose. Doing this actually caused my coolant reservoir to be over-filled, leading me to have to suck some coolant out.

Today it was 57 degrees out and this is what I observed:

Highway: NA
Neighborhoods: 198-200 degrees
Idling for more than 10 seconds: 205-210

My guess is the black 180 degree thermostat Atlantic British sold me isn't really opening at 180. Seems more like 190+
I guess I'll just have to live with 210 degrees at idle. I hope my head gaskets and cylinder sleeves can live with it

 

I think that is what happened to me. As soon as I bought the genuine 180 stat, my temps dropped by 30 degrees!

 

I got a bad one from AB as well about 6 months ago

 

SOLVED!

Did what cvhyatt did. Factory 180 thermostat installed (replacing non-oem 180) and temps are down 20 degrees.

Cheap ($33.00) thermostat by Britpart had me running way too hot:
Expensive OEM ($85.00) thermostat and I'm cool as a cucumber: