Wow. Tough stance.
Throw away $5K or more trade in loss because you are too cheap to buy some aftermarket temp gauge?
I also note my temp gauge is higher than the real temp outside.
Usually I can tell if it is below freezing. Something I picked up walking outside once in a Blue Moon I guess.
My car is parked in a heated garage, so the temp drops from 78F/68F (year round) down/up to whatever the temp is outside in a minute of so. It stays higher than the real Winter temp by about 8 degrees I guess. Summer it seems to be right on actually.
I might try to change it to Celcius temp range and see if that is correct.