If you want to get decent milage the US needs to start getting low-sulphur diesel and SOON, so that the newer generatiosn of Diesel engines can be brought over.
a VW lupo diesel will do 60mpg, an audi A8, with a 4l twin-turbo diesel can manage 40mpg on the highway (and thats a big heavy car!)
I also agree that driving style has a lot to do with it - I did a run from atlanta to sailsbury, NC on sunday - there and back averaged
30mpg, on a vehicle with an EPA highway rating of 26, and the return journey had 2700lb of lexan in it. That was from an 87 dodge 3l, with the check engine light on, imagine what i'll get when i get the engine working graet (i got it about 4 weeks ago)Basically comes down to 3 things
1) driving style - most americans, it seems, have little knowledge of smooth driving, or wide spacial awareness. they don't anticipate or aggregate. The significantly lower standard of driving required to pass the test in the US compaired with the UK, also means that drivers look for bigger vehicles for safety.2) Mechanicals - American engines are not the best out-putters of power. Tend to be big engines, that are then tuned for low-end torque and made quiet. The abundance of automatic boxes also makes it less efficient. Side impact bars, safety cages etc. are also often missing in the smaller cars, meaning that peolpe look to the big heavy vehcles for safety.
3) legislative. Car tags, at least here in georgia, are priced on vehicle value, in the UK, they're emissiosn dependant. Smaller engined cars cost less. the lower safety requirements, and the incrased reliance on active, secondary devices, such as airbags, and away from better stronger chassis, or better handling (admittedly, the last is hard to legislate) . Silly stuff too, such as Arnie proposing the Pruis be allowed to use carpool lanes, even when only 1 person in it 9the prius's 1.5l engine, is the same size as that in my civic, and my civic is a HELL of a lot lighter with no batteries or motors to feed/carry - so can i run my civic in the california carpool lanes on my own too, eh? nope, didn't think so.