How do modern cars regulate temperature so well?

couple comments=

My stock 73 318 will stay at 165 all day in all conditions in super hot and humid FL city/mixed driving.
Sunpro gauge and IR agree.

Turn on the AC, though.......

I have a "Scangauge II" unit that will read degrees frm the sensor on an OBD II car. This can be used to determine "normal" and other points on the factory gauge. It also reads and clears trouble codes, and calculates MPG.