LML Poor fuel mileage when towing

[tbelue]

Hi Guys,
Still getting used to the dmax. 2012 LML, first long trip towing our toy hauler,30 foot work and play loaded up to 12K. First tank went 9.96 mpg next fill was 8.6 mpg. Neighbors 2008 gets about the same or worse towing his fifth wheel running the speed limit. Both trucks are stock except for CP3 and fass pump.
What is the best mod to increase MPG while towing?

 

[DefiantArms]

Efi live?

What speed where you running?
What terrain?
Were you in regen?

 

[chevor]

Speed limit:rofl:

65 mph tops better economy, 60 mph about the best.

I have heard a topper on the bed can really cut down wind resistance.

 

[Hoojs12840]

I have 2016 3500 crew cab 4wd. Towing my 17,000 5th wheel with a combined weight of 25,000 I get 11.8-12.3mpg average depending on city and mountains. Cruise set at 62 as much as possible.


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2013 GMC Sierra 2500 CC 4WD
2016 Jayco Northpoint 377RLBH

 

[tbelue]

65-70mph and some hills and some flat, not alot of flat land in Alabama.

 

[Hoojs12840]

That would be part of the issue. Anything above 60 is going to be a cost benefit analysis. Is it worth getting there a few minutes sooner vs. saving money?

My trucks completely stock, I'm not sure what the two things you changed would do to MPG.


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2016 GMC Sierra Denali 3500 CC 4WD
2016 Jayco Northpoint 377RLBH

 

[tbelue]

I had 5.9 Cummins and the worst it got was 10@ 75-80mph best of 14mpg @60mph. I was expecting similar mileage. Guess its time to look at a MPG tune on EFI.

 

[dmax_ty]

The Cummins also wasn't saddled with emissions equipment that negates fuel mileage.

Look into tunes, but also changing your driving style will fetch the biggest mileage gains.

 

[Blackmax123]

My lml dually lifted with 295/70 r 17's averages about 7.2-8.5 towing 18k up and down the hills of central pa. Running 70-75.. problem is now they've raised all our highway speed limits to 70 mph. And I'm not gonna be the idiot riding in the right lane doing 60 mph that all the truckers have to swerve so they don't run over you.. so I don't pay attention to my milage, I just put the fuel range on the display and I stop about every 200 miles and get fuel.

 

[mpeters0991]

I've got a lmm and I pull a 34' wildwood toy hauler and it will weigh in about 14000, so with the truck I figure I'm around 22000-23000 and both times that I've hauled it around southeast Iowa and northeast Missouri I've gotten 7.5 to 9.5. One trip I took it up to Iowa City and had a head wind both ways and didn't get any better than 8.5. I was really hoping to see double digits but don't know if thats going to happen.

 

[The Engineer]

With my 2013 2500HD Duramax towing my 24ft enclosed race car trailer (8500 pounds), I typically get 9.5 to 10.5 MPG.

 

[Hambone]

Simple answer...
Delete and tune
Air intake
And when towing, keep it 5th gear for anything over 6k
Just my opinion:thumb:

 

[WVRigrat05]

I get 7-9 towing 12k and I'm fully deleted in 35's, I keep it at the floor on 90% of the hills, and run 70-77 mph. Only towed with the LMM twice on a stock delete tune.

I got the same, sometimes a tad better with the LLY with same set up on a 120 tune.

 

[Dsword]

Low miles on engine?

3000 miles on new 3500 dually. Pulling empty containers. 50 to 55 mph on hilly and curvy two lanes, 62 to 65 on interstate. Getting 6 mpg either way. I can't wait for it to break in... At least I think that's what the problem is. Or maybe it's that big flat front catching all the wind. When I pulled my 34' 5er to storage I got 10-11 mpg.

Should add that 40' container weighs 8300 and trailer is 1500, truck a little over 8000, so just under 18000 total.

 

[GMC_2002_Dmax]

With my 2013 2500HD Duramax towing my 24ft enclosed race car trailer (8500 pounds), I typically get 9.5 to 10.5 MPG.

Exactly what I get towing my 24' enclosed at 10K lbs.

:thumb:

 

[Kblazer87]

.
Should add that 40' container weighs 8300 and trailer is 1500, truck a little over 8000, so just under 18000 total.

You have a 40 foot deck gooseneck trailer that weghs 1500 pounds? That doesnt seem correct.

 

[07keo02]

My lml dually lifted with 295/70 r 17's averages about 7.2-8.5 towing 18k up and down the hills of central pa. Running 70-75.. problem is now they've raised all our highway speed limits to 70 mph. And I'm not gonna be the idiot riding in the right lane doing 60 mph that all the truckers have to swerve so they don't run over you.. so I don't pay attention to my milage, I just put the fuel range on the display and I stop about every 200 miles and get fuel.

What are the truckers running that they have to "swerve" out of the way to keep from running over a pickup/trailer combo doing (what I would consider) a very reasonable 60 MPH?

On another note, these mileage claims dont have me overly anxious to get out of my 6.0 (gas) and back into a duramax.

 

[DangerousDuramax]

What are the truckers running that they have to "swerve" out of the way to keep from running over a pickup/trailer combo doing (what I would consider) a very reasonable 60 MPH?

On another note, these mileage claims dont have me overly anxious to get out of my 6.0 (gas) and back into a duramax.

Your 6.0 cant tow what a Duramax can and your unloaded fuel mileage is much worse as well. So if your pulling light loads and that's what the truck spends most of its time doing then your golden. Otherwise you're loosing money by driving the gasser and have a weight and speed limitation compared to a Duramax or any other diesel for that matter. If you load up your truck and an identical truck with a Duramax and the same heavy load behind them your gasser will suffer far worse mileage.

 

[Awenta]

Can't knock the six.oh it's a great engine. If you don't pull heavy all the time then there is no reason to switch.


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[bmc1025]

Can't knock the six.oh it's a great engine. If you don't pull heavy all the time then there is no reason to switch.


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Agreed, not to mention if you blow it up your only out 2k.