I have a '85 380SE and my gauge barely goes to 60°C when on the highway/expressway. In city driving, it goes up to about 80°C and when idling in drive for a period (10 minutes), it will rocket to 110°C. Then back down to nearly 60° (sometimes 55°C) on the freeway. I am sure my thermostat is broken. A new one is $30. vs. $8. for my 95' Suburban and it looks like more work to change- which makes me crosser still. NABD though.

I am sure someone with a car like yours will reply with a more detailed analysis of what your car should be registering.