I think I have posted on this before. MPG is more a matter of how you drive than what you drive. Even a 400 HP Corvette can get pretty good MPG if driven well.
2009 Chevrolet Corvette MPG Test Drive: Will the Vette Meet New CAFE Standards? - Popular Mechanics
Now I personally have no use for anybody that drives 10-under the posted limit. In my view they are as big a hazard as the aggressive driver. FWIW, my sim agrees with the link. Driving the limit would get about 30 MPG.
Now if the ‘Vette were available with the 4.5 liter diesel V-8 GM had to drop, 50 MPG would be easy.
Too bad Corvettes are so headroom challenged. I could get a distressed C5 or C6 and convert it to a Cummins 4BT3.9 and put some even lower rolling resistance tires on it and probably get 40-50 MPG easy.