The cts is nice, i love mine. But he aero isn't very good. 90% of my driving since 6/1 has been straight highway with very few stops, i keep the fuel log fairly up to date in the garage here.
If you want a 4 door with good aero, though not light, the dodge intrepid can fairly easily be swapped to rwd.
https://youtu.be/yi0An09-skE