Ideally the temperature should hover around the middle of the temp gauge range. Usually somewhere around 85˚C. It will move around with load on the engine and ambient conditions (outside temp, A/C on or off, etc). Depending on what the thermostat is doing and how well the cooling system works, you can see it move between 80-100˚ and still be within normal.

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Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]