[Joebie]

Its going to be tough to replace a RWD car with one that gets good gas mileage as RWD = sporty and sporty more often than not mean sacrificing efficiency for power.

If you're ok with a FWD car (yuck) i would consider a used

-Corolla Hatchback
-Mazda3
-VW Golf
-Civic SI


The only RWD cars that immediately come to mind are

-Toyota GR86 (not sure if these are terribly efficient, but they look good and are sporty)
-Mazda Miata
-Lexus of some sort? I'm not overly familiar with the Lexus lineup but i think the IS250 and e90 might have some similarities. Its a 4-door sedan that looks pretty decent, similar power, and comes in RWD or AWD. I dont think they get amazing MPG though, but not bad MPG either.

Hope this helps and good luck!