[The law states that a speedometer can be inaccurate by plus 10% to minus zero.
Yes, that's correct - but personally I would like my car to show max +1% - as a physicist, I'm very opposed to be given deliberately false readings.
That is also why I bought oversize summer-wheels for my Espace, which has given it approx 1% overrreading, which is more acceptable. :-.)
That said, my Murena has always been very precise, - never under-reading, but mostly been less than a few (3-4?) percent. So even old-fashioned, cable-driven speedos are capable of sufficient precision to enable such small overreadings.
I testdrove a Citroen C2 and a C3, when they just came out - and using GPS we measured both of them to do 88.0 km/h when the speedo showed exactly 100 km/h - that *is* pathetic, but I'm convinced it has to do with the maybe somewhat optimistic fuel-economy promises.
/Lennart