Filled up and did a short empty non-towing " semi Highway trip" Some stop and go on a four lane Highway a few lights toward the end. About 135 miles round trip, the computer said we were getting 19.4 at one point. It mostly was saying average of 17.4 while we were at 55 to 65 mph. It seems to be getting better and we only have 1300 miles on it so far.I did an oil and filter change at 1,000 miles Rotella 15w40. I will go with synthetic Rotella after a few more oil changes. I'll post again after I do the math on the last trip. I think maybe about a 16 mpg overall so far best guess.