even this past summer around town, I'd have to be sitting a while for it to climb to 100 ish. Now as it is cooler out, I'm not getting quite to 80C. Should I replace the t-stat?? It's got a fairly new radiator and fill of coolant. I did a flush a while ago also, probably 5 years. Thanks!

Look at the following thread and I'd recommend you do what I did. Read post 2

changing coolant

Look after your investment. You're do for a flush and a thermostat is so cheap I'd replace it anyway. Mine failed and caused a coolant explosion:

Please Help!!! Coolant Explosion!!!

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1989 300CE Astralsilber/Schwarz
1992 300CE Schwarz/Schwarz

For some reason, my temp gauge "sticks" a little - it runs about as you say, unless I tap the console, at which point it rises 10-20 degrees (to something more "normal").

That's the exact procedure I used last time. *sigh* I guess it's that time again. I don't want to fork over the $$ for MB Citric acid, but I do want something stronger than the Prestone. Maybe I'll just read labels and get the best of what's there at wal-mart.
Thanks for the suggestions. Now, which brand t-stat to get? I have found Wahler, Behr, and maybe a couple others, all within about 3 dollars of each other.
TIA

Before you rush to get a new T-stat and MB coolant, please make sure it is not the temperature sending unit (TSU). Mine was running at 60 C all the time and I spend $$$ to get the T-stat out only to find out it is in a perfect shape. The problem was the TSU.