I am new to this site but have been a Cummins mechanic for quite awhile. I bought a 2007.5 3500 srw longbed. My fuel milage at best on the freeway was 14mpg I only have 3000 mi on it and I am now in Iraq . When I get home I would like to make the best mods for fuel milage only. I am happy with the power, any suggestions?