F150 diesel 4x4 is 25mpg highway, rather than 30. I read an article (Jalopnik maybe?) that broke it down - while the 4x4 has more underbody stuff to cause aerodynamic drag and some parasitic losses, it also comes with more kobby tires with a higher load rating.
I wonder what sort of economy I could get with this engine in my Insight.
Wouldn't that be a hoot.