Note that it is "ambient outside temperature"...otherwise, it would fluctuate noticeably with driving speed/wind temperature, etc.

Also note that while sitting in traffic on hot days, it WILL pick up a few degrees from the engine heat...

...and although you don't have an inside temperature gauge, your car is equipped with an inside temperature "sensor" that interfaces with the climate control system.

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car