I just rolled over 20000 miles today on my 6.7 with the 68rfe and have to say I love this truck. I haul around 10 ton of hay and other farm items probably 4 to 5 days a week and have had no problems the only issue i had was i tried to straight pipe it and didnt put the sensors back and had to take it to the shop and get it reset after i put the cat and dpf back on. Mileage has improved as it has got more mile and it gets about the same as my 06 did 8-8.5 loaded heavy and 14.5 to 15 empty.