MPG Increace
I don't get why some are being hard on the OP or insisting on another car. He stated in the beginning he wants to drive his car as a daily driver and not interested in another car for that. I think he's smart enough to realize that an econo box will be more economic for him. He seems like he's looking to get a few more mpg without reinventing his car. And I don't know people keep on insisting to compare the mileage for our ABodys with civics and such, a more apples to apples comparison would be new Chargers, Challengers and such.
Things to improve
Aerodynamics
Lowering
1.5% rake
Front air dam
Weight
Lowering cars weight
Lower rotational weight
Driving habits
Vacuum gauge
Tune up
A/F gauge
Oil and gear fulid like royal purple
Check the plugs makes sure your burning all your fuel
Electric fans
Under drive pulleys
Measure exhaust back pressure your shoot for 0
If you do a lot of highway drive an overdrive can give you the most rewards, or you could have a weekday gear set and a weekend set if your running an 8 3/4.