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2020 6.6 D-max towing MPG

Lfod1836

By Lfod1836
in 6.6L Duramax Diesel (L5P)

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I recently did a 1300 mile trip from Ohio to South Carolina and back pulling my 9k lb travel trailer. I averaged 10-11 MPG at around 70 MPH through the trip. If the traffic wasn't so bad through the mountains, I could have pretty much set my cruise and maintained highway speeds up and down the grades. Super impressed with the performance of the truck.

 

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Lfod1836
Lfod1836

That's actually really encouraging! Considering I can't even get 10 MPG with my 16' LTZ 5.3 pulling my 6500 lb Jayco at 55 mph. It has the 8 speed and will never even think about going into 7th g

Lfod1836
Lfod1836

I understand MPG is not why anyone gets a bigger truck with a diesel. You can buy a lot of fuel with that $9k additional diesel premium. My #1 reason for the bigger truck is safety in pulling my

cNate
cNate

2020 GMC Sierra AT4 2500 Duramax towing 9k bumper pull travel trailer. I’m seeing about 10 MPG all around, when I haul from sea level to Eastern Sierra Nevadas (8k foot climb) and back. Averaging 65-7

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TheeSpaniard3500hd Enthusiast

TheeSpaniard3500hd

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Just finished our big summer trip from Seattle area to redwoods, San Francisco, Sequoia, Yosemite, Lake Tahoe and Crater Lake.  Averaged 9.8 for the trip pulling a 7800 travel trailer.  Lots of elevation and switchbacks seemed to impact the mileage.  Truck towed great. 
 

 

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  • 5 months later...
James Wiler New Member

James Wiler

Posted
Posted

Your mileage will vary significantly depending on usage.  The Duramax doesn't like stop and go.  It'll do 15ish.  I've towed a 3,000# trailer from CO to East TX and averaged 28mpg running 75mph.  The trailer was a tandem flat bed so very little air resistance.  Going back with a 3,500# tractor on it that had an enclosed cab, hence lots of air drag, I got half that.  Pulling my 35' 15,000# 5th wheel (13.5' high) I get 10-11 at highway speed.  Your DEF consumption will also vary A LOT.  Under load it'll use way more than running easily.  Hope that helps.  Let me add that the Duramax is an awesome engine, truly amazing!  It has no problem accelerating on on the grade up Wolf Creek pass towing that 15,000# 5th wheel.  The temperature of the engine and transmission only climb 2-3 degrees.

nutdriver Enthusiast

nutdriver

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Posted

I normally average about 12-13 mpg towing a 5000 lb travel trailer.  My typical highway speed is around 65 mph.  I have averaged as much as 15 in the high plains of Wyoming and Montana over 500 miles.  Wind makes a huge difference and living in Kansas that is often a factor.  Towing into a headwind or even a quarter wind will drop my mileage below 10 mpg.  Likewise towing with a tail wind is a big help.

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