Next time you see one of those portable radar units that law enforcement often parks on roads that have a high incidence of speeders - you know - the trailers that have a big display of "your speed" - check the display vs your HHR's speedometer. You will be able to verify all of the information in the many responses above.

 

Mine reads approx. 61 (looking at needle) when the unit reads 60. Noticed it tonight when I passed one of those.

 

You could just find a place with one of those traffic cams and speed past it. I think your speed will be printed on the ticket you get in the mail along with your picture for your collection.