Originally Posted by jbell36
i'm just trying to be realistic...i was hoping my 6.4 would get close to 18 or so after i tuned it...and when i say i tuned it, i mean EGR delete, DPF delete, all new exhaust, and a cold air intake...i run it on the 275 tune which apparently is the best tune for fuel efficiency...the best MPG's i ever got was 16.3 doing about 80 on a 5 hour trip, so all highway...all city i get about 13.2-13.5...these are real world numbers, and i sunk well over 2k into it...i do remember the guy who helped me install it say he thought the down pipe has a leak in it, and i have 126k miles on it, so who knows how well the injectors are working, but no serious signs of anything going wrong, other than it's starting to smoke a little more than usual while driving casually, you used to not be able to see any smoke at all if you didn't want to, now it smokes at every acceleration...
slow down to 65 mph and accelerate easier meaning use less throttle. I would bet you will crack 20mpg if not higher. slowing down is one of the easiest ways to get better fuel economy. my buddy has a 6.4 extended cab short bed with 3.73 gears and he just got back from a trip from ct to nc and got 26 mpg hand calculated. and consistently gets 25-26mpg in the 275 tune egr delete and dpf delete as well. he also bought his truck new and only has 45000 miles on it.