with a good EFI live tune you can easily get 18-22mpg with an LBZ, heck i was getting 18 bucking the wind all day today, I know I love my LBZ more than I did my 05 5.9, plus I really love the growl the duramax creates when you slam the skinny pedal down

 

I just drove 1265 miles from Michigan to Tampa ran 70mph the whole way. I got 21.9 mpg hand calc

 

My dad has a 07 duramax and it gets about 18 on the highway unloaded no mpg tune. and 22 with mpg tune at 75-80 mph. When he's hauling hay or his trailer it gets about 12.5 with out the mpg tune and about 15.5 with the mpg tune

 

There are to many variables to consider. I recently sold my 02 cummins dually 4x4 excab auto with 4:10s. This truck would get 17.5 every day all day. I replaced it with an 06 lbz cc, sb, 4x4 that gets 17. this is w/out a load on both trucks. lbz has 5" exhaust and 135hp ppe tune neither of wich changed the mpg. the dodge had straigt pipe and afe cold air and raptor pump.

 

my old 06 i was getting 26-29 mpg on the highway keeping rpms under 1800

 

I call BS on this, was this hand calculated or from the DIC?