So I have 2000k miles on my Duramax and have been loving the engine. I drove it home initially from Oregon to Idaho highway mileage averaged close to 30mpgs and was ecstatic.
Just took a trip to Oregon coast and towed fairly light travel trailer (5000lbs) about 500 miles, mostly highway. I averaged about 10.5mpgs. Kept reseting the miles cause I thought this was incorrect. It was windy, and I wasn’t super heavy on throttle.
Way home, wind was light, driving conditions perfect and still averaged 11mpgs. I was expecting much better mileage. Any suggestions on why my mileage was so poor??