i had an 07 6.0 and now an 11 6.2 and the milage is only slightly worse with the 6.2 im gettin 15 driving to work on a mix of country roads highway and a little city driving but thats being easy on the pedal and keeping on about 60, 8.3 towing travel trailer the 6.0 i had wud get 16-17 and 9.5-10 doing the exact same thing both trucks had 3.73 gears