Problem on Thrust

[ana-t.]

Here's an off-the-wall physics question.

 

1 - If the Wil E. Coyote put an Acme rocket on his car, how many pounds of thrust it would take to start seeing better miles per gallon?

2 - Or, would 50 pounds of thrust have enough effect to notice? How about 100 pounds?

Vehicle has a 0.25 coefficient of drag (car), and weighs 4500 pounds.

 

I would really appreciate your help. Thank you.

[elfmotat]

Any thrust at all is going to yield better MPG, even if only marginally. There's no cut-off you can point to and say "the car starts getting significantly better mileage at x lbs. thrust."