I did the exact same thing as you man.... Driving from Oklahoma to El Paso ! For the first 750 i let it shift through gears and drove it easy.... Right when i hit 750 i gunned it from 70 to 100mph.... And from there on every now and then and at every rest stop i stopped at gave it a little through the gears.... I managed to get 17mpg on the highway breaking mine in like that... If you wanna get crazy on so offroading here let me know !!!