On a recent trip, we calculated our Ford's fuel mileage at a dismal 9 mpg when averaging 75 mph, thanks to 5.38 gears and 40-inch tires. At that rate, our tank would be sucked dry in only a few hundred miles, and we would be stopping for fuel every few hours-taking precious time away from our Mad Max-style road trips.
Clearly something had to be done, so we visited Zylstra Automotive in Visalia, California, to have one of Zylstra's auxiliary fuel tanks installed. We were looking to more than double our capacity, and its bed-mounted design fit the bill. We opted for the Fuelbox model, which is a 58-gallon tank that comes with a very usable toolbox attached on top of it. The tank had quality welds throughout, the toolbox had its own separate floor rather than the top of the tank being the tool tray, and it was made of extra-thick aluminum so we could put some weight on it if we ever needed to. The tank also was compliant with all current DOT laws and had its own pump so we could turn it on and off when necessary. Best of all, the tank wouldn't alter our existing fuel system all the while increasing our range from about 250 miles to more than 700! These tanks can be installed by Zylstra Automotive or ordered as complete kits (pump, wiring harness, and so on) for the do-it-yourselfer. Follow along while we triple our range and gain a toolbox too!
There are many different options and tanks to choose from. An L-shaped tank offers a larger toolbox while taking up more bed space. We opted for the tank with the toolbox on top for our Ford. | 
The stock filler neck had to be modified with two fittings so the fuel can be pumped into the stock tank. The second fitting is for a return line, so if the auxiliary tank's pump is left on, fuel will just cycle through the system instead of overflowing. | 
Our new Fuelbox looked much better than the old propane tank we previously had, plus it's mounted flush with the bed so a cover or camper shell can be installed. The tank is mounted in three places on the bed to maintain a solid foundation but still allow the tank to flex if the terrain gets rough. |
The first step to the install was to remove the filler neck from our Super Duty. | 
These fuel tanks also have two fittings for a return line into the top of the tank and an air vent for safety. | 
Note the clean installation of the auxiliary fuel pump, wiring, and lines. Since it's under the vehicle, take care of it if your truck will be running over rocks or plowing through the snow. |
A small wiring harness for the pump and pump controller attach right on the firewall of the engine compartment. | 
A fuel controller is mounted inside the cab on the dash and indicates whether the pump is pumping or not as well as the level of the secondary tank. The pump can also be turned on or off manually from here. | 
All Zylstra tanks come with cam lock latches that pull the lid down firm with the top of the toolbox to keep dust and debris out. |
The toolbox came in very handy because we can now put everything that was rolling around the floor of the truck into a secure place-with room to spare! | 
The fill neck for the Fuelbox is located inside the toolbox and fills just like you would a normal tank. | 
Tanks are also available with hand-fueled pumps that can be locked inside the toolbox for safety and security. |
The bed is also modified for the fuel lines and wiring to run through. Note that everything runs through pressed-in grommets so nothing will get cut or frayed by the bed. |  | |