I used to drive a truck that, when babied, got a whole 18 mpg. City driving made it plummet quickly into the 12mgp range. Most sports cars (unless it's got a V10-V12) get better fuel economy than this. In fact, some of the innovations in sports cars (the Audi R10 for one) increase fuel economy.
On the note of fuel economy, and the like, what is the point of 10% ethanol gas. My car runs worse, gets less mpg (around 10% less mpg). Is it just an excuse to dilute the fuel, and charge the same for it? I know it reduces emissions, but when I have to use more to go the same distance, it seems like it isn't doing anything helpful. Much like the "hybrid" cars, that cost you more than they'll ever save you in fuel (fuel savings for 3 years is usually around $3000, the replacement battery in 3 years is around $3500-$4000), and the technology to make the batteries is also harmful to the environment.