There is also a MPG difference requirement based on the type of vehicle being turned in versus the type being bought. My co-worker traded in his old Honda Pilot for a brand new Acura TL last week under this program ($3500 rebate) and just got a letter that stated that the TL did not qualify because the MPG difference was only five, and it had to be 6 or more. "Return the car or pay $3500 more." He's going to return the car, and then see if it shows up on their used car list!
Ahhh bureaucracy at work. I wonder how much it's costing to have an army of auditors sit around somewhere and generate/mail letters for 1 MPG overages.