Analog Speedo VS Digital Display (Info screen)

[ZGadson]

Ive been wondering for a while now, why there is a difference between what the analog speedometer says and what the digital trip computer in the dash says.

On the highway, I can set the cruise at 75, then reset the trip computer to find the car's average speed only to see that the speedometer says Im going 75, and the trip computer says Im going 60.

I've checked the tire size - its the correect size for the car - and I've tried setting the cruise at other speeds and checking the trip computer. If I set the cruise at 40, the trip computer says 39. If I set the cruise at 90, the computer says 81. The faster I go, the further off the speed is.

Anyone else notice this? Which one is more accurate?