The 3.0 get better gas mileage in higher rpms. I think 4.10's are better for it. What will increase mileage is accelerating slower and driving slower in general.
My grandpa get 29 mpg city/highway with his 87 Grand Marquis (5.0) by driving like, well, an old man. Thats how you save the MPG.
Last edited by Dangeranger3; 06-16-2008 at 08:28 PM.