Yeah, but the whole 4-cylinder thing may seem all Mr.Wizard and oh-so-efficient, but the facts most folks happily overlook are these:
When you put a small engine in a heavy car, force it to make power similar to a V8 by winding it up tight as a cheap watch and adding turbochargers, etc, you're stressing the small engine MUCH more heavily than you'd stress a larger one to get the same result. This tends to make the entire system very complex, complicating service, and shortens the unit's life span.
Couple this with the unfortunate and widely ignored fact that to get as much power out of a small engine as you get from a large one, you simply have to cram as much fuel and air through it as the big one burns. There ain't no free-energy lunch, and the small engine really isn't going to return significantly better fuel economy figures than the larger one.
A small engine in a LIGHT car can be vastly more efficient, but a highly-stressed small engine in a 2-ton hog is an exercise in doublethink.
But yeah, why let the realities of engineering and physics interfere with your opinions, and the feel-good marketing positioning of a small engine?