Ok I've owned a number of GMC Sierra's. 4.8 V8 (01) , 5.3 V8 (2012 & 2014) I tow a 22' Rockwood Minilite travel trailer...fully loaded for a vacation it is around 5800 lbs. It is a high trailer so it pushes a LOT of wind. The 5.3 V8 returned no better than 10.5 MPG and that was never pushing beyond 62-65 MPH.
Fast forward to my 2017 Canyon 2.8 Duramax...pulling the same EXACT trailer...18.5 MPG ... That is the good news...now I am experiencing some bad sensors the last sensor upon replacement only lasted 8500 miles. My total mileage is 32,100 so jury is out we'll see if GM honors the powertrain. So far so good...
The truck is a dream when it is running without issues...
