Haven't tested the M3W properly but on my Aero the odometer on a normal 58 miles run I do regularly shows about 63 or 64 miles so on this particular car the odometer is linked to the speedo (which overreads about 8 - 10% most of the time) and find it surprising that the M3W is different.
On my M3W the speedo doesn't seem too far out so perhaps it's just the built-in safety margin and the calibration of meter to wheel size is basically ok.
