As has been said, speedo's MUST over-read when they leave the factory. It's illegal for a manufacturer to sell a car that reads slower than you're actually driving so they compensate by adding a good 7-10% on. However, funnily enough they do seem to 'come back' at higher speeds. My dad's car is like 10% out accross the usual speeds to 70 but bump it up to 150 and it matches his GPS... interesting. I've just been done for speeding on the M6, doing 86 which musta been reading like 94 on the speedo. Oops. I blame the rental car company- was supposed to have a 1.6 focus and they upgraded me to a 2.2TD Mondeo ST. Meh.