I need some info guys.

[Mike Murphey]

My '06 got around 14 in town and 16 on the highway...I put a programmer in it and it got 17 on the highway....

[BpsDaddy]

I noticed an increase in my 7.3's when I started adding cetane to my fuel every fill up. I wonder if that would do the same for a 6.4? There are little things that I would do to my new truck. Like add a program to it, and change the exhaust from a 3" factory to a 4" which help also. I am still up in the air.

[Mike D]

There are still not a lot of aftermarket upgrades for the 6.4 because of all the emissions garbage on it and unless you know the service manager really well, I would hesitate to modify it until you are out of warranty. They are very picky about mods to the new trucks.