[MadisonMPG]

Originally Posted by Backtobasics

I have a 97 Ram 5.2 5 speed.
K&N airfilter in stock box
headers, converter, and exhaust
electric fan.

If I keep it under 65, I am high teens, low 20's with no eco driving techniques.

I'd check current state of basic tune up. Plugs, wires, air filter, etc.
I'd replace stock muffler.

Bear in mind, 3.9 in FS truck is a lot of weight to move. Easy throttle, and hypermile techniques should help.

Is that mostly highway?