Are you sure?
How did you measure this? Best way is to use a 'good' thermometer stuck in the center vent.
Also due to the engine heat, it's natural that it heats the air venting so that it may be a little bit warmer by the time it gets through into the car.
So it sounds normal, although 8-10 F may be a little too much. What happens are highway speed, after everything cools down. Is there less differential under those conditions?
Regards . . . . JimF
'94 S500 Cpe
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