I just bought a new MB OEM thermostat from the dealer for my newly acquired 300CD Turbo. The old one was stuck open and the car never got above 50C. The new one runs it at 90-95C constantly.

The radiator is brand new and since I know the cooling system is in good enough order to keep the car running at or below 50C all day long I can say conclusively that this new thermostat is keeping it running at these temps by design in my opinion.

I didn't look too closely at it for a makers mark or temp reading but the car does not overheat...it never goes above 95C and seems to run fine at that temp, so I am leaving it alone...FWIW I think there are some that keep them at 80C but I do think the MB factory model intends them to run 90-95C now for some reason.

__________________
Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz