Most EPA number is lower than their EU or even Canadian equiv....TBH I actually found EPA number to be relatively more accurate in most cases. EPA does seem to skew more with electric/hybrid though.
Also to note, OEMs supply the number and test results to EPA. EPA just ensure their test procedure conforms to the standard. But the trick is in the allowable "fudge factor" to account for drag/rolling resistance and whatnot. And that is where OEMs tend to be more liberal and the number tend to inflate more. Though recently with the debacle with Hyundai and Ford's number being questioned, they might dial those back a bit...
It is interesting to hear my friend talking about this since he works for a company that does 3rd party benchmarking for OEs on competitors....
University of Toronto Formula SAE Alumni 2003-2007
Formula Student Championship 2003, 2005, 2006
www.fsae.utoronto.ca