The Europeans are so lucky, they get all the good stuff...
In Europe Subaru is releasing their brand new first ever boxer diesel engine, and they say it's capable of 60mpg. Not sure if that's American or British MPG figures, but either way it's good. Here's a first drive by Edmunds.com

http://www.edmunds.com/insideline/do...24553?imw=Y#17

The good news is that it 'might' come to the US someday...