http://www.nytimes.com/2006/03/30/automobiles/30energy.html?_r=1&oref=slogin&pagewanted=printsnip
For two decades automakers have been developing technology that could make vehicles go farther on a gallon of gasoline. But instead, they have chosen pep and size — making vehicles like the new Murano accelerate faster than cars like the old Mustang, and making them bigger.
The average vehicle, which 25 years ago accelerated to 60 miles an hour in 14.4 seconds, now does it in 9.9 seconds, a pace once typical only of sporty or luxury cars like Camaros and Jaguars. And vehicle weight now averages about 4,100 pounds, up from about 3,200 in the early 1980's, as many buyers switched to larger, roomier cars or to sport utility vehicles and minivans, and as automakers added safety equipment
snip
Buyers like the extra zoom and room, but these have come at a cost: average fuel economy has fallen slightly over the last two decades. The government's new standards for light trucks like S.U.V.'s, published yesterday, will require an 8.1 percent increase in miles per gallon over the four model years from 2008 through 2011.
snip
If 2005 model vehicles, with their better technology, had the performance and size of those in 1987, they would use only 80 percent of the gasoline they do today, according to the Environmental Protection Agency. That alone would get the country nearly halfway to the goal President Bush set in his State of the Union address: to cut American oil consumption enough to nearly eliminate the need to import from the Middle East.
==========
See
http://www.ucsusa.org/clean_vehicles/cars_pickups_suvs/ on how it is fairly easy to build more fuel efficient vehicles.
http://www.ucsusa.org/clean_vehicles/cars_pickups_suvs/building-a-better-suv.html specifically shows this for SUVs. "A September 2003 report from the Union of Concerned Scientists, Building a Better SUV: A Blueprint for Saving Lives, Money, and Gasoline, shows how existing technologies can be used to offer consumers an SUV that is safer, cleaner, and more cost-effective, while retaining the size and performance SUV drivers have today."