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?