I drove from Indio to Parker AZ for Thanksgiving. Used cruise control 70mph and as I was paying for gas used 87 and in 580 miles round trip got 15.1.MPG. In December I drove from Indio to Tempe AZ and as someone else was buying fuel I used premium. Same speed, a lot of the same road (I10) and same load, just me, and same weather conditions with no other changes to the truck, for a 770 mile trip I got 18.4MPG. So that is about a 18% increase in fuel mileage for about a 6% increase in fuel cost. Am I missing something? And the "seat of the pants meter" felt she ran much better too!!!