I own 3 vehicles, I'll list them from best to worst MPG:
2005 BMW Dakar - Eh, its not a car, but I get over 70mpg on the bike. With 70lbs of camping gear on the back, I get mid 50's.
2006 TDI VW Jetta - I'm not a big fan of VW's, but the new jetta is bigger then the old jetta, and its a fun car to drive. I get ~44mpg around town, and saw 47mpg on a long freeway only road trip. My main reason to purchase was the engine, turbo-diesel; I expect the car to last me 300,000 miles, or more.
1997 Jeep Wrangler - 12 to 15 mpg... I havent started the jeep in 2 months, its a summer toy only.
Other then that, I ride my bikes alot, i run a small bike site, www.bikeforums.net