Hello

Water pump was leaking,replaced WP and thermostat 87C with Zerex G-o5 coolant.
Now the temp. stays at the 100C mark before it was staying just past the 80C mark the old thermostat was 87C. I drove the car around let it idle for 1hr. with heat running before it went to the 100C mark in summer time stop and go traffic. It's 27F outside right now. Any thoughts. Car is 95 E320 176k mi.
thanks

__________________
1995 E320
1998 E320
1999 E320 4Matic
2000 E320 4Matic
2000 ML320
2007 C230 Sport
2003 Cadillac CTS