Here's the drag coefficient calculation for y'all to play with:
http://www.wolframalpha.com/input/?i...2F17.3ft%C2%B2
Now here's the problem, as Orange4boy correctly points out. This very aero car expends about half its energy overcoming rolling resistance at 60mph. If the Crr is only known to within 20%, the Cd can not be known in any meaningful way.
For Crr=.006, Cd=.194
For Crr=.008, Cd=.151
For Crr=.010, Cd=.109