I have the same issue with my speedo.

The odometer is dead nuts on but the speedo reads fast. The error on mine gets worse at higher speeds. When the speedo shows 40 I'm going 45, at 60 I'm actually going 70 and at 70 on the speedo I am travelling at about 83 mph.

I've confirmed this with GPS and stopwatch. I've considered just moving the needle but for now I just do the conversion in my head.

__________________
Joe

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1980 300SD - 495k miles - 'The Ambassador'
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Former Family Members
95 C280
73 280SEL
90 300D
87 300SDL (X2)
86 560SEL
84 300D
80 300SD