How do check speedometer calibration 1996 Dodge Intrepid?

Answer 1

find a stretch of federal free way and drive at speedometer reading of 60 miles per hour for 10 miles . have a passenger with a stop watch measure time between mile markers. record the time you get on the stop watch, a watch reading of less time of 60 seconds will tell you that you are going faster than the speedometer is reading if it is 57 seconds (five over) or if it takes more than 60 seconds per marker it is reading (5 under).
60 divided by the seconds of a stop watch times 60 will tell you miles per hour.
60/ 57(stop watch reading from marker to marker) x60 equals 63.15 miles per hour.