They report , every extra 100lbs of weight decrease fuel economy by 1%(including people tools etc)I now have 5,000 plus miles and have never been over15.5 MPG. Took it in and found nothing. Only asked if I use Premium which I have from the start. I carry at least 1,000 lbs of tools and never am on the highway. All my work is within 10 miles of my home. The shift points seem to hold on to long so some times I force it to go to a higher gear. Not happy since it was a reason i sold my 1 ton NV3500 for the 11MPH it gave me. I also seems to surge when you ease on the gas from a start or rolling away from a stop. I have to watch it or my tools wind up on the floor.