I've discovered that my analogue speedo is about 4 km/hr out. For example if I set my cruise control on when the speedo reads 100 km/hr, my satnav (not the inbuilt one but an external Garmin unit suction cupped to the windscreen) reads a stable 96 km/hr. This reading from the satnav is corroborated by doing an average speed reset on the MID while cruising. It reads 96 km/hr also.

Is this common ? That the speedo reading is overstated ?

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2001 X5 4.4i