Yes, all of the speedos read Higher than actual depending on your tire diameter/size.
~3 mph faster.
It helps keep your speed down a bit and many times I have been glad it has as I cruise by an unseen CHP a little on the high side.
(Radar Detector ordered before its too late)
Your allowed 10% over actual by most police unless they are feeling ornery or are just plain bored.
They are generally not amused when you mention that due to the rotation of the earth you are already traveling ~300mph plus or minus your speed depending on direction.
If they offer to write you up for 300mph, accept, so that when they show up in court and cannot demonstrate to the Judge how they added or subtracted your cars speed vector from the 300, it will get thrown out.
Plus the judge will want a demo in your 300 mph Porsche
and you can frame the ticket and put it up in the garage as a conversation piece.
