Some cars require premium gas. So its an added cost. That's your concern isn't it? If gas was $1/gallon mpg wouldn't matter.
How about the up-front cost. Just a hunch, but I'd bet the Audi, Acura, Mustang, Lexus, and Volvos will cost $5000 or more up front.
If you're so concerned about 4mpg or whatever why didn't you get a Prius?