"You can pick lots of good reasons [yeah like wvo!] for increasing the fuel capacity of your diesel pickup. With an extra tank in the bed, you can shop around for the best price on fuel, and load up for a really long haul. (In fact, you can extend your range so much that you'll probably need to stop for human fuel several times before your truck needs replenishing.)"

http://www.dieselworldmag.com/content/view/52/36/