GPS mph accuracy

[mountainman]

Originally Posted by mountainman

I have 3 Porsches and all 3 do the same. Somewhere from 2 to 4 MPH less than the gps shows.

Must have had a senior moment, or I have sniffed too much of the paint I am brushing today. Meant to say the speedo reads more than the gps on all 3. It is hell getting old, but there is only one alternative...

[schnellman]

Like everyone else, my speedometer reads 3 to 5 miles per hour faster than the GPS. I had a deputy sheriff clock me on radar one day just to make sure. The GPS is right, the speedo is not.