For good MPG and tons of fun you can't beat a Shelby GLHS. Mid 14s out of the box, mid 13s easily attainable, handling that you will not believe, and MPG in the high 20s if you stay out of boost. I drove mine to Ocean City averaging 80MPH and got right around 28MPG. Very decent used Charger GLHSs can be had for under $3,000.00 and you have the added bonus of having a very rare car.