just completed a 2260 mile trip in my 6.4 Laramie-saw everything from 11 mpg to a brief time at 20 mpg-final tank was 17.3-truck ran fine (knock on wood)-did the first oil change at 2950 miles-wal mart has the 0W40 Pennzoil-it is not cheap,26.58 for 5 quart jug and had to buy 2 (no singles on hand) for my 7 quart change-like the truck!