Hi. I find it very interesting to read about fuel efficiency. My truck is a 03 2500 dodge 4x4 quad cab cummins with 35" tires 3" lift with some aftermarket upgrades like afe cold air intake, 4" exhaust aeroturbine banks tecnicooler air ram, BD super turbo single, BD exhaust manifold, snow performance water injection kit, 50 hp injectors, smarty programmer running it 90hp up, 4.56 axles, Garmon 48re trans triple disc converter.
I have a hard time to get more than 15 MPG that's running empty between 65 to 70 with lots of slowing down and speeding up on a 250 mi. trip with a little heavy right foot. So I'm thinking all my upgrades don't help me much for fuel efficiency other that it is a fun truck to drive with all the power it has. All those after market parts sure don't help as much for fuel efficiency as advertised to my opinion.