Thank you for your reply Klaus! I did the flywheel adaptation run tonight, or at least I hope I did (I don't have a Volvo Systems Tester for seeing the adaptive values and knowing when they have stabilized). I just guessed that 8 decelerations from 3000 ~ 3500 rpm in 3rd gear with the foot off the gas pedal should be enough.

I'll try the first drive cycle tomorrow. The 240F estimate for the red zone sounds right.

On my gauge the first of the two red marks is the 10th index mark. When the car is warmed up and the ambient temperature is around 50°F the needle points to the 4th or 5th mark around town, and at interstate speed it points to the 6th mark (about the 3 o'clock position).

The car still has the original 90°C (194°F) thermostat (113K miles). I don't know whether "90°C thermostat" means it starts to open at 90°C or that it is wide open at 90°C.

If the thermostat is keeping the water circulating inside the block (not through the radiator) until the needle is close to half way, then wouldn't the half way mark be warmer than 122°F?

On a cold morning when the needle is at the bottom, how warm must the coolant be before it starts to move up?

Is the temp gauge connected directly to the temperature sender, or does the signal go to the engine computer which then tells the gauge what to display? The latter is the case on my Saab to prevent nervous owners from being alarmed by dramatic temperature gauge swings as the thermostat opens and closes.

Would appreciate your additional thoughts and knowledge about this very much.