Butch59

Hey everyone. We have a 2017 6.6 diesel duelly with 74k miles. At 73k we had 8 new injectors put in, oil change, new fuel and air filters, values cleaned. 6 new tires properly pressured. We are pulling a 37ft 5th wheel, also with new tires properly inflated, no water on board. We drove 9k miles last year out west and got on average 11mpg with the 5th wheel heavier than this year. We have gone 1k this far on flat roads, averaging 60mph and we are steadily falling in mpg. We started at 11.2 and now at 10.3. what should I be looking at? We are heading west again for another 9k trip, we are only 1k into it. Do injectors need break in time? Should I have the oxygen sensors looked at? Appreciate any input!!