The MB spec thermostat for these cars starts to open at 87C and should be fully open by 92C. If memory serves me correctly, high aux fans should come on at 107C then go off again when temp drops to about 100C. (low aux fans are triggered by ac refrigerant pressure only)

During hot weather city driving with the ac on, both my cars (94 E320 wagon, 95 E320 sedan) settle in around 95c--needle at the top of the 8. When stopped in traffic, it is not uncommon to see the temp bump up to the aux fan trigger point. My sedan has a resistor that lowers the aux fan temp trigger to about 100C. Sitting in traffic, I can tell by the temp gauge when the aux fans have started.....

I believe temperatures in the 90C to 100C range are normal for summer operation with the ac on.

As far as the markings are concerned, I have always thought the mark between 80 and 120 is 100. But now that you ask the question it does make me wonder a bit.

Forum member Jim Forgine has some really good information on the aux fan story. Here's a link to his site. (Jim--hope you don't mind)

http://pages.prodigy.net/jforgione/MB_CTS.html