I just got 47 mpg highway in my girlfriend’s car. [...] How is it that the Fit is only getting 38 highway in such a dinky little econo box?

Ralph, the fact that you "just got 47 mpg" doesn't mean that the Yaris generally gets 47. Firstly everone gets better mileage on summer blend gasoline. Secondly, under certain conditions your car can do a lot better than it's rating: I've learned I can get low-40s mileage in my 2007 Fit on a long highway trip.

The Yaris is rated as more economical than the Fit, and I believe it. My guess as to why is that the 2007 and 2008 Fits sold in the US have first generation engines (going back to 2001), while the Yaris since 2005 is a second gen model with, presumably, a more economical engine than its predecessor.

Honda engineers can do better than that.

I'm sure you're right, and they plan to: