Gp didn't call it speeding though. Interstates in the US often do have an 80mph limit, which is in turn routinely exceeded. That doesn't change the fact that 80mph is vastly less fuel efficient than 50mph, which is a typical speed for a two lane highway. Americans (and Germans?) simply don't want to acknowledge that speed kills efficiency, just as incessant speed changes kill efficiency, although the latter is mitigated by regenerative braking.