Compare speedo speed to SatNav speed (pretty much accurate with open skies)

Make a mental note at 10 mph increments, or get you navigator to note them down.

See if is consistent across the range.


Obviously make sure your tyre pressures are correct.

Speedos can be set for a set Rolling circumference, if they changed wheels and tyres set up from when they specified the original scaling to the speedo scaling.

When you mess about changing tyre sizes this can have an impact as can simple tyre wear.

My Roadster is the most accurate setup I have ever had at 70 mph the Speedo is showing 70 mph whereas my supposedly modern Toyota over reads woefully (making the annual mileage clock up quicker!) almost sounds like a deliberate measure to give high mpg figures if you were cynical like me wink

Mark - No Longer driving
Archie the Old English Sheep Mog...........
2010 Roadster 3.0 V6 (S3) wink