6.0L gas RE vs mpg

Depending on where you are staying, fuel blends can also make a difference. Winterblend gas always knocks my mpgs down.
My 6.0 with 4.10s gets about 13 mpg unloaded and maybe 15 on the highway. Our 6.0 3.73 that we use for work is really about the same. Yes, fuel economy has also been known to increase as new engines go thru the break in period. And of course, the old standard, driving habits have a lot to do with it too. I honestly don't think changing to a taller gear of any ratio is really going to make a noticable difference with this model. The 6.0 is just known for power and poor mileage.

APT wrote:
Does 1100 miles on this 6.0L mean it is a new 2014 model with 4.10 axle?

My 6.0L broke in and reduced fuel consumption after about 20k miles. I bought in October, got 11-12mpg all winter. This winter which is far colder is netting 13mpg. Towing the first summer was about 7mpg. Second summer was 8mpg. We have done a few 1000+ mile non towing trips from 6500 miles on the odo to 38k and have had up to 18mpg. So I think yours will improve somewhat.

2015 GM 2500HD Dbl Cab, not 2014, yes, new two weeks ago. It shows around 15-16 on the highway empty first 500 miles, and when I popped the TC and hit the highway again - it slowly dropped (Of course, carrying 3200 lbs now) it went to 10.5 mpg -- so, it runs great and hauls great, but I was a little disappointed in the mpg. I'd hoped to haul at about 12 mpg at least. My 2003 and 3:73 hauled TC weight at 11-12 mpg. Even with the 4:10, I'd expect with the new tech stuff at least equal to the old 6.0L and 3:73 ...

SO, hopefully it will improve. One other thing too -- after about a week, the start began sound weird - instead of kicking right over, it winds a bit, numerous revolutions, and coughs, then starts. Not every time, but maybe 20% of the starts.

Actually sounds like fuel issue or a spark issue, so that might help as well. Will give it another 1000 miles, then take it in -- or maybe sooner if this 'cough/start' keeps at it. Does it more often in cold-damp weather. As if moisture is impeding the spark, although have no clue how moisture would get inside anything ...

Does 1100 miles on this 6.0L mean it is a new 2014 model with 4.10 axle?

My 6.0L broke in and reduced fuel consumption after about 20k miles. I bought in October, got 11-12mpg all winter. This winter which is far colder is netting 13mpg. Towing the first summer was about 7mpg. Second summer was 8mpg. We have done a few 1000+ mile non towing trips from 6500 miles on the odo to 38k and have had up to 18mpg. So I think yours will improve somewhat.

While not an exact comparison, my 2009 2500HD with 4.10 rear axle got 14 mpg empty, and my 2013, 3.73 rear axle gets 16 mpg under the same conditions. Both with the same engine/transmission/body. The ten percent or so improvement would not be worth spending the money for.

I really am not sure it will make that big of a difference. I don't have a truck camper so I can't say what mine would get. I get 8.5 towing a toy hauler converted enclosed trailer that weighs about 8000 lbs. I get 15 on the highway with an atv in the back and another atv on a 5x8 single axle trailer. and I get 11-12 mpg mixed around town.

It sounds like you already know the answer to your question as you have had the 6.0 with both 3.73 and 4.10.

With only 1,100 miles the MPG's will improve over time. I expect the owner's manual even directs you NOT to tow much for atleast the first 1,000 miles of break-in if not more. I think the overall lack of miles may be more of a factor at this point than the gearing when the TC is in the back.

Nobody switches from 4.10 to 3.73, everyone wants to go the other way. Say the gain was 10% (I can't believe it would be more) and you drive 15,000 miles/yr. At 10.5 MPG and $3.50/gal your fuel cost for the year is $5,000. A 10% improvement would save you $500/yr. Switching both rears in a 4x4 can't be much less than $2,000 so the break even mark is 4 yrs, towing performance suffers, and the next person who buys your truck would likely rather have the 4.10's.