Ahhh, essentially a network administrator like me!
Man, you DO have waaaaaaay too much time on your hands! You gotta stop futzing around with this drag coefficient stuff & defrag something. Funny, this almost sounds like the paradox of trying to go faster than light: the closer you get to traveling at light speed the more the mass of the object grows so that you cannot theoretically attain the speed.
A question, Tom: as the car moves forward & the air is passing around & underneath it it should create a 'lift' similar to an airplane, hence the spoiler. I can only assume that the spoiler doesn't completely cancel out the 'lift factor' so how do you figure that into the equation? I would think that makes the tire resistance slightly less the faster one travels.