[Big Dave]

Just a word of encouragement.

I just spoke with a guy who has a 94 Caprice. The Chevy B-body is very similar to the Ford Crown Vic. Maybe a couple hundred pounds lighter. 305 cubic inch TBI V-8. 4L60 automatic. 2.56:1 gears in a GM 10-bolt axle.

He claims AVERAGE 29 MPG and the car is essentially unmodified.

So 40 MPG is not that far off.

Roughly average hypermiling
A ruthless weight reduction program
LRR tires (orobably Goodyear Fuel Max or Michilin HydroEdge)
3.08 or lower gears
A diesel engine
T-56 transmission
Grille block, belly pan, fender skirts, MoonEyes, some sort of rear deck treatment

That should get you there.

This guy's success tells me I could get 30 out of my Imp with a gas engine (L92), a T-56, and some aero mods.