>>>*I have spent a lifetime dealing with airflow and what it really does, sometimes I think I still don't fully understand it.

But some modern vehicles have drag co-efficient ratings that actually should be impossible mathematically.

I know my Corvette has a rather hi-tech engine and management system. There is a mileage counter on the dash that gives readings every couple of seconds. With a tool like that one can relearn how to drive, and the system adds just enough fuel to certain cylinders to make enough power to hold the speed..coasting it just shuts it off entirely.

Plus that machine is rather slick in the air and as speed increases it lowers closer to the ground by quite a bit.

Oddly, at 75 MPH I can make the counter read right around 33 MPG, at 55 MPH the best I can get is right at 30 MPG.

The difference is ground effects and less air being pushed.

One thing I did notice, in our Monte Carlo I can draft behind a big truck and the air around gets quiet, plus I have to back off the throttle to hold position.

The Corvette doesn't draft behind trucks worth a hoot, the air spilling around makes it move back and forth. It is best out in clean air or following at extremely high speed, I have run up tight to other Corvettes at double nickle speeds and she likes that.

I can easily believe that good ground effects and streamlining is worth 25% in mileage savings and more at crusing speeds, especially on a boxy type vehicle....*EB