Turbo 3000D. I put one on and it paid for itself in less than a week. From RI to Scranton, PA to Rocky Mount, NC. Grossing 76.5 and getting with the program. I noticed AT LEAST 1 MPG improvement! So, i deadheaded upto richmond, VA, picked up my next load, hit the "J" in ruther glen, VA to top off the tanks. when i left, i set the cruise @ 65, ran across I-64 to STL and arrived @ my destination (Columbia,MO) with a little over a half tank left.
I have an '05 Int'l. 9400 w/ 450 Cummins ISX, 10 spd. Prior to install, my truck averaged 5-5.3MPG. Less if i was heavy and running the hills, mountains, or high elevations.
What i'm saying is this, without ANY change in driving habits, I saw a 1+MPG increase. The increase goes way up if I stay close to the speed limits. Last week i ran just over 3300 miles and put approx. $683 in my pocket in fuel savings!