Fuel economy conspiracy theories are silly. If American customers cared more about it, not as an abstract thing but as a practical spec in purchasing, a lot of these crazy advances people claim are being suppressed would be implemented immediately. Well, if those things even work in real world conditions. Mod an engine and you could post some truly ridiculous numbers, but does it hold up in start/stop? Does it last as long as a traditionally designed engine? Lots of people into this conspiracy theory seem to assume the number happened once, and from there it's just putting it in cars.