You can pick lots of good reasons 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.)

Not only that, if you have other diesel engines that require refueling in a remote area, you can add a pump-out nozzle to your "ready tank" to keep them supplied. Having extra capacity is also an advantage when towing because of the increased rate of fuel consumption.

There's yet another aspect to consider. With the increasing use of home-brewed biodiesel, having more capacity allows you to load up on this friendlier fuel if you don't have access to it on a long trip. Todd Smith of Extreme Biodiesel decided to add a 100-gallon tank to his rig. The tanks has a toolbox integrated into the top, so now he has plenty of biodiesel for his trips to the desert with a toy-hauler in tow.

Whatever the reason for adding a second tank, Aero Enterprises recommends using manual valves made of brass and Teflon to control the flow. After years of fabricating fuel tanks of all sorts--including replacement tanks for every domestic make of truck--the company feels that manual valves are the safest, longest-lasting and most dependable way to operate a fuel system. You control which tank you use first, and you'll always have a way to get home on one tank or another. And you'll also know how much fuel you have onboard because there's a separate gauge for the auxiliary tank.

Aero's Jake Jackson feels that the drawback to using a gravity-feed system into your factory tank comes if there's a problem with fuel contamination or clogging.  Once that happens,  it affects all of fuel. Also, with an electric valve, it's better to install a pair because there's no advance warning when one fails.

Another point in favor of manual valves is the warranty. When used with diesel fuel, electric valves have no warranty. Aero has a one-year warranty, but Jackson says he hasn't seen them fail even after 10 or more years of use.

As an extra measure of protection, Aero supplies a large in-line Fram fuel filter/water separator with its bed tank. In addition, the company's toolbox/tank combinations are made entirely of aluminum (not a steel tank with an aluminum shell). Prices range from $900 to $1700, and that's with installation included. All of Aero's tanks are welded in-house with internal baffles, and then pressure tested with air prior to installation. Drain plugs are included as well, should you need to clean out the tank.

Aero offers tanks for wide variety of applications, in addition to factory replacements. So even if you need a custom setup, the company can probably meet your need for extra fuel capacity.

This combo tank has a toolbox under lid, which also protects the access to the fuel fill. The sending unit fits is installed under the access cap at the left corner.	Note the quality of the fuel fittings on the concealed side of the tank.	When the toolbox lid is closed, the fuel filler is protected and out of sight.
An optional pump-out system can be installed as well for providing fuel to other diesel engines, or to simply transfer fuel from the auxiliary to the main tank if you don't have a valve system. Another option is to fill the main tank with conventional petroleum diesel and put biodiesel in the other tank. That way, you can add the percentage of biodiesel you prefer as needed.	Before installing the tank, drill a hole in the bed for routing fuel lines. Be sure to install a rubber grommet in the opening to prevent chafing.	Since it's made entirely of aluminum, the Aero Tank is fairly easy to lift into place.
Route the line through the new opening in the bed.	Drill holes from underneath (so you don't have to remove the foot well carpeting) in order to install the manual valves.	Install the valve handles on the floor, just forward of the driver's seat.