What year and model? For most MBs, the thermostat is supposed to start to open at 87C and be fully open at 102C. Anywhere between 80C-100C should on the highway should be normal.

__________________
Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record