How do i make my mopar a daily driver??

TrailBeast said
I was getting right at 17mpg on the hiway with a basically stock 4 barrel 318 and 904 transmission at 75-80mph.
When I went to the 5.9 Magnum with a 42rh overdrive trans that went to 25mpg on the hiway at that same 75-80.
I went to a bigger cube motor, but bringing the RPM's down on the hiway made the difference.

A 500 RPM reduction on the hiway is 30,000 less cylinders filling with fuel in an hour of driving.
That's a lot of fuel.
Click to expand...
What do you think helped the most in MPG/ the 5.9 engine (lower RPM) or the A500 overdrive ? When your on a fixed income fuel mileage is important. A vehicle that sucks fuel like a pig..does not get driven much.
People say "smiles per gallon" but I guess they have more money to buy more fuel, someday they may not be able to spend as much on fuel...then they may change their minds/or not.