EPA estimates are based on ideal conditions. No one ever drives in ideal conditions. When I see an EPA estimaged mpg, I always automatically subtract at least 5. Also, what IYAMCNDN is very important to this thread. Canadian gallons are different from US gallons. Gotta watch out for that on these forums.

 

I think the mileage estimates are done on a dyno, road and ignore the static air resistance. There are changes in the work.