2019 2500HD Duramax Towing Fuel Economy

[vranasaurus]

I recently purchased a used 2019 CCSB Duramax 4wd with 70,000 miles.  I pulled my 24 foot enclosed bumper pull cargo trailer on a 1460 round trip through Kansas, Oklahoma, and Texas. 
 

On the way out the total weight of the trailer and cargo was approximately 8500 lbs and on the way back it weighed approximately 6900 lbs.

 

On the way out averaged 7.9 mpg and on the way back averaged 7 mpg.  On the last 200 miles back there was a considerable head wind and I only got 6 mpg.

 

The only modification I am aware of is the previous owner installed 275/70R18 tires in place of the stock 265/70R18.  The difference in tire size is about .5” in diameter and 1.5” in circumference, not a significant difference. 
 

Do these fuel economy numbers seem low?

 

I was getting about 6mpg pulling similar loads with my 2015 1500 with a 5.3.  I was hoping to get at least 10-11 mpg while towing these types of loads.  Were my expectations too high?

[calgator73]

26 minutes ago, vranasaurus said:

I recently purchased a used 2019 CCSB Duramax 4wd with 70,000 miles.  I pulled my 24 foot enclosed bumper pull cargo trailer on a 1460 round trip through Kansas, Oklahoma, and Texas. 
 

On the way out the total weight of the trailer and cargo was approximately 8500 lbs and on the way back it weighed approximately 6900 lbs.

 

On the way out averaged 7.9 mpg and on the way back averaged 7 mpg.  On the last 200 miles back there was a considerable head wind and I only got 6 mpg.

 

The only modification I am aware of is the previous owner installed 275/70R18 tires in place of the stock 265/70R18.  The difference in tire size is about .5” in diameter and 1.5” in circumference, not a significant difference. 
 

Do these fuel economy numbers seem low?

 

I was getting about 6mpg pulling similar loads with my 2015 1500 with a 5.3.  I was hoping to get at least 10-11 mpg while towing these types of loads.  Were my expectations too high?

With my long gone 2015 GMC Sierra 2500 with an LML the 10 to 12 miles per gallon towing a 37-ft travel trailer was very common only occasionally did I drop down to 9.  Biggest impact for me was regeneration of the DPF.  Small things like electric brakes dragging a little bit or poor aerodynamics on the trailer or even excessive speed on your part could dramatically increase your fuel consumption.

[CamGTP]

How fast were you going?

[vranasaurus]

3 minutes ago, CamGTP said:

How fast were you going?

Averaged between 70 and 75 MPH.

 

 

[CamGTP]

Anything over 65mph is going to start tanking fuel mileage. You are towing a massive brick afterall.

[vranasaurus]

14 hours ago, CamGTP said:

Anything over 65mph is going to start tanking fuel mileage. You are towing a massive brick afterall.

I agree with you that faster speed will decrease fuel economy due to air resistance. I’ve pulled similar loads with similar aerodynamics with my previous 5.3L 1500 and got 6 mpg.  I just want to make sure my truck isn’t consuming excess fuel for some reason that could be addressed.

[CamGTP]

Next time you need to tow that trailer do your own MPG loop. Even if it's only like 50 or 100 miles total. Drop your speed to 60-65 to see how big of a difference it makes.