I have seen a few threads here on the LML where people were banging on their poor fuel mileage. I had to put a word in here about what I have found.
This is my second Duramax and the 04 did very well on mileage so I was concerned that the 14 with all of the emissions crap would have crappy mileage. I found that it won't quite reach the 04 but it ain't bad.
I made a 2000+ mile round trip to turkey hunt in Kansas. I hand calculated mileage for the first couple of tanks but when I found that my math was within tenths of what the truck was telling me it was getting I stopped doing it by hand. The truck averaged 20.4 mpg going and 19.6 coming. Generally there are tailwinds going and head winds coming home so 20 even for the trip. I generally was at 80 mph on the Interstates and 70+ on the back roads.
The 04 on those trips would be about 24 mph average.
A little different story pulling the toy-hauler last week camping/hunting. It is all uphill going and all downhill coming. Going up was just under 7 and coming down was almost 10 (still a few big mountains to climb but most of it is downhill).
So, overall I am happy. I was a little worried when I was reading threads where people were only getting 15.
2014 Chevy Silverado Duramax LML Crew-cab LTZ, short-bed, 4wd.
Fumoto Drain Valve
Air Lift Loadlifter 5000 Airbags
Kennedy Lift Pump
Sold: 2004 Duramax LB7
2011 3010 Heartland Cyclone HD 35' Toyhauler