I think you are going to spend a lot of time chasing something that is normal. you cant compare an old tired thermostat to a new one. There are numerous threads about this very issue and they all come to the same conclusion. A new 80c thermostat is going to have the car anywhere from 85-100c for a normal day.

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1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual