I pass two local police department "safety reminder" speed display units on my way to/from work each day. If the day is rainy (Subaru day), my speedo agrees with their display of my speed. On sunny (Boxster) days, my speedo indicates 3 MPH higher than their units. I guess I could just be happy that I have a 158 MPH top speed Boxster instead of the 'normal' 155
, but...
Does anyone know if it is possible to have the dealership easily check/change the speedometer's calibration?