2 MPH Speedo error

<div class='quotetop'>QUOTE(ken1784 @ Aug 4 2007, 01:16 PM) [snapback]490549[/snapback]</div>

Ah ha! Eureka! I get it now. I have been perplexed by this problem for a while and this is the 1st answer that makes sense to me.

I have checked the odometer against the highway mile markers several times over long distances and they were always pretty close. I have done the same with my other car (2001 Olds Intrigue) with the same result. However one time when both cars were following each other on the highway the Prius was showing a speed 3-4 mph higher than my Intrigue. I thought, how can this be if the previous odometer checking showed they were both about the same?

I never considered that the speedometer is running separately from the odometer!