1700 RPM is the magic line for my '09 2500, Quad, 4x4, Auto, LB. Under it, you can get 19-20 empty/14-15 with the cattle trailer if you have a soft foot. If you want/need to run over 65mph it will drop 14 empty/11 full or lower. I had the same truck but an '05 w/5.9. Both bought new and while...