I drove my 2020 Sierra 1500 with 4wd on a 2,100 mile round trip starting with 8,000 on the odometer. About 200 pounds of cargo. It averaged 27.7 driving about 75-78 mph most of the way. All highway miles. That was calculated with gas receipts and miles driven. Meter in the truck read a little over 26 mpg. I was very happy with it.
I took my Silverado 1500 4X4 on a short trip yesterday (159 miles round trip). Unloaded, not towing anything, and with mostly Interstate driving, it returned 30 MPG. (Confirmed by filling it up before leaving and after returning and hand calculating the result.).
I’m impressed. It beat its EPA highway estimate by 1 MPG. Great engine!
So far my unloaded in-town driving has netted me about 24mpg. Looking forward to how towing performance results we hauled our loaded 5700lb Toyhauler 430 miles to Poteau OK from Abilene. Wasn't very impressed with the fuel mileage (13.7) but considering I had a side wind I figured that was close with a new engine. Power was great but transmission has a tendency to constantly shift when it shouldn't.
Return trip was worse...12.1 mpg calm winds. Shifting has become more erratic and now it won't hold 1500 rpm instead it stays up around 2000. This engine is designed to run at 1500 which is where its producing max torque. Taking it back to dealership in morning and see if they can figure it out.
FYI...my 2015 Ecodiesel avg 15.5 - 17 mpg towing the same trailer from Abilene to Utah, Nevada and home.