[lunarhighway]

a quick google revieled an article claiming an 0.32 Cd for both the sedan and the coupe, seems high for the coupe as the cobalt is esentially the emerican equivalent of the opel astra G (same platform differnt body) the astra coupe has an 0.28Cd without a spoiler where the sedan has a 0.29.

the chevy seems to sit a little higher off the ground than the opel (possible softer american suspention vs the astra's hard euro setup?) and with FE not being so important for this type of car in the US (as you say yourself you doubled your milage with this car so chevrolet doesn't need to squeeze every last mpg out of it)

i think the spoiler might add 0.02 or so to the Cd, just a guess though....

loosing the spoiler is possibly the best for FE...beause "real" spoiler are only there to allow for extremely fast cornering wich doesn't matches well with FE driving anyway

than again, if you like it... just drive carefully with FE in mind and you should see a very decent milage on that car anyway