Originally Posted by Kai

You'll run into drag problems around twice the legal speed limit. You don't need to be going that fast.

The coefficient of drag for the hatchbacks is right around .33.

For reference, my RX-7 comes in at ~.30 (.29 if some of the original aero parts didn't rust off,) and the Honda Insight comes in at .25. A Miata, with the top down, is around .38.

All in all, the EF body cars have decent aerodynamics.