Regarding the accuracy of any speedometer, be aware that this will vary with the age of your tires and their wear impacting the overall diameter. The best source of tire information I've found online is at TireRack. I've found many of my assumptions about tires proven incorrect using their research, which they actually perform.
Try the link below, then click the Speedometer Accuracy
link. There's a chart there you can use to verify your speedometer.
[quote="garygid"]I thought (do not know the law or ruling) that the US requires the manufacturer-displayed speed readings to be a percent high, and Europe requires more, like perhaps 2% high. But, I could be wrong.