First, take a look at the tires/rims on the car and compare to the manual to see what it should have. That could be part of the problem with the MPH reading, the odometer could be showing only partial mileage due to age/wear. The odometer on the 108 was only registering approximately 50% of the distance driven until I had the speedo head rebuilt.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.