My 03 F250 super duty 4 door 4x4 7.3 powerstroke turbo gets 20mpg highway 18 city. But I've added some extras. Advanced air intake, oversized exhaust, 6 position power programmer with up to a 140 hp boost and a bulletproof tranny. I drive from Alaska to Texas and back every year. Spend summers in Alaska and winters on the gulf coast of southeast Texas. I've 140k on it and it runs like new. I seem to get the best performance at 70 hp boost. I just change the oil every 3k miles except when I'm driving between Alaska and Texas since its 4500 miles so I'm going to try Royal Purple oil next time since you can go 5k between oil changes this is the best truck I've ever owned