I have noticed a difference in the fuel since I filled up the last tank. This time I filled up at a station that touted premium diesel and my mileage per gallon increased again. This time running at just over 65 to 70 mph I am getting 18.3. This with having to run some hills but not pulling a trailer.I do feel that the quality of fuel and the type of driving has alot to do with the economy. I have enjoyed the vehicle so far, it has been a while since I have had a new vehicle. I now have just a little over 1500 miles on the odometer, the miles are cranking up a little to fast for me, don't want to use it up all at one time.The fuel here is around 2.35 to 2.37 per gallon, I am in Fort Worth Tx.