You wonder how they only get 43mpg? Here's how:
"The most popular type is the Family Sedan ... Six-cylinder engines are the norm, but smaller sedans might have four-cylinder power and larger ones a V8"
I'll add that they almost always mate that six-cylinder to an automatic transmission, which conveniently absorbs most of that power.
Many of their engines are also technologically challenged; 2 valves per cylinder is common, as is fixed valve timing, and ohv. In many ways they're using a scaled up version of our engine technology from 25 years ago.
When I was last over there I took a Ford Mustang for a test drive. I was really impressed when I turned the engine over and the whole vehicle twisted with the torque. Sadly in use it was rather similar to driving a 1.6 Focus with the steering disconnected ;)
They do also use a different gallon to us...