Here is the list of the 2006 top sellers, by volume, for the U.S. (list courtesy of Edmunds). I have added the average fuel economy numbers from the EPA's 2007 fuel economy list.
1. Ford F-Series (includes F-150, F-250 Super Duty and F-350 Super Duty) — 796,039What I see in these numbers is that the love affair for large vehicles continues, despite fuel costs. Where is the landslide towards small thrifty cars? It isn't here yet.
Fullsize and just plain huge trucks.
Ave. fuel economy: 17mpg (V8 combined City and Highway numbers)
2. Chevrolet Silverado (includes 1500, 1500 Classic, 1500 SS Classic, 1500HD Classic, 2500HD, 2500HD Classic, 3500HD, 3500 Classic — 636,069
Fullsize trucks.
Ave. fuel economy: 17mpg (V8)
3. Toyota Camry and Camry Solara — 448,445
Midsized car.
Ave. fuel economy: 29mpg (I4)
4. Dodge Ram (includes 1500, 2500 and 3500) — 364,177
Fullsized Trucks.
Ave. fuel economy: 17mpg (V8)
5. Honda Accord — 354,441
Midsized Car.
Ave. fuel economy: 29mpg (I4)
6. Honda Civic — 316,638
Compact Car.
Ave. fuel economy: 35mpg
7. Chevrolet Impala — 289,868
Large Car.
Ave. fuel economy: 26mpg
8. Toyota Corolla — 272,327
Compact Car.
Ave. fuel economy: 35mpg
9. Nissan Altima — 232,457
Midsize Car.
Ave fuel economy: 30mpg (I4)
10. Chevrolet Cobalt — 211,449
Compact Car.
Ave fuel economy: 28mpg
Of the top ten best sellers, approximately 2,160,000 units (F150, Silverado, Ram, Impala) get worse than 28mpg (CAFE target is 27.5 for cars). 1,835,100 units (Camry, Accord, Civic, Corolla, Altima, Cobalt) get better than 28mpg.