I'm an 'old-school Pontiac guy- my first car was a '65 GTO tri-power convertible 4-speed. Had a '69 Judge with the Ram Air IV and a M-22. Now have a '69 convertible I'm restoring. I worked for PMD as a rep in the late 70's, and IMHO, the Grand Prix hasn't been built since 1977.;) Something to do with size, hood length, plastic, body cladding, fwd etc.

mpally- I realize you are looking for something that will get you some gas mileage over driving a truck. I used to drive GM, but have had so many fall apart on me in the last couple of decades, I won't own another late model.
I now drive a VW Jetta wagon with the TDI engine. I drive 150 miles round trip to work (highway miles in/out to Chicago, and am getting 40+ mpg. An amazing little car for a diesel, and it's performance is very surprising.
Very safe, German made, and fun.

For those Grand Prix drivers, for less than $10K (if you are patient in your search) you can buy one of the SMOOTHEST rides ever designed by a Detroit company. I had a bunch of them from '69-'72's, and they are my favorite car next to the GTO.;) :)

My sister drives a 2001 (or 2002) GT. POS. Brakes, transmission, electrical (headlights go out mysteriously when they feel like it) water leaks in trunk and interior, etc. etc. I wouldn't wish one on anyone.