why in the world does the 6.7 get such worse fuel mileage than the 5.9 even without the egr? i thought i would be gettin close to 20 but i was wrong. i thought this would improve with the engine swap instead of get worse.....

 

The 6.7 has twice the smog equipment than the 5.9. Also how many miles do you have on the motor? I didn't get good mpg's until about 18k due to breaking it in.

 

Delete all of the emmsions and put on a bigger exhaust, my boss did that to his 08
19.5 on the highway with cruise.

 

extra fuel is used to clean the DPF when needed and Nox