370z speedometer vs computer trip avr. speed

super_fla

while driving at constant speed and reseting the speed average on the comp. trip, it calculates different speed reading!!

speed average should be the same as the current speed if it were constant , but it reads lower by about 6% !!

i know the speedometer is not that accurate, but since its the same car it should read from the same speed sensor. does our car have more than one speed sensor ??

if you lost with what im trying to say please see the video below



by the way, the same thing happens with my 350z i previously owned.

and measuring the speed using mobile GPS readings gives the same results on the computer trip avr. speed

can someone explain !!