[j.fro]

Here's my experience on the same question; looking forward to input. I've got the Dash Command app and the elm wifi transmitter. In my 1999 996 C4 on 95+ degree days I'll see coolant temps stabilize around 216 running 71 on the highway. In highway traffic accelerating/decelerating, temps get to 221, but no higher. On cooler days, temps never get that high.
How hot is too hot?? 225? 235? 245? 250?
FWIW, my 986S with center radiator and hood vents never gets over 219, and cools down to 180 quickly once we're moving.