In-Bed Auxiliary Fuel Tanks
What an In-Bed Auxiliary Fuel Tank Is
An in-bed auxiliary fuel tank is a fuel tank that mounts in your truck bed and feeds your truck's own fuel system, extending how far you can drive between fill ups. It is not a tank you dispense from with a nozzle. It exists to keep your factory tank full.
For anyone who drives long distances, works away from fuel stations, or wants to buy fuel where it is cheap rather than where the needle lands, an auxiliary tank turns a 500 mile range into a 1,000 mile range without changing anything about how you drive.
Auxiliary Tank or Transfer Tank?
These two get mixed up constantly, and the difference is simply what the fuel is for:
- An auxiliary tank refills your own truck. The fuel goes from the bed tank into the factory tank.
- A transfer tank dispenses fuel to something else: equipment, generators, machinery on a job site. Those use a pump and a nozzle.
If you want both jobs done, look at truck bed transfer tanks, which are DOT approved for gasoline, diesel, kerosene, methanol, and aviation fuel and can be set up with a pump.
Diesel and Gasoline Work Differently
This is the fork that decides everything else about your setup, and it comes down to federal rules about where fuel is drawn from the tank.
| Diesel Auxiliary Tank | Gasoline Auxiliary Tank | |
|---|---|---|
| How fuel moves | Gravity feed, no power needed | Inline electric pump |
| What you install | Fuel Shotz kit through the factory fill neck | Inline pump on the frame, toggle switch in the cab |
| In daily use | Nothing to do, factory tank stays full | Flip the switch when the main tank hits a quarter |
| Included with the tank | Install kit sold with the tank | Pickup and return fittings built in, pump not included |
Gasoline cannot gravity feed because federal rules require gasoline to be drawn from the top of the tank. That is a rule about the fuel, not a limitation of the tank. Full detail on the diesel side is in our guide to how gravity feed fuel tanks work.
Which Install Kit Fits Your Diesel Truck
Diesel auxiliary tanks use the Fuel Shotz kit matched to your truck's fill neck:
| Your Truck | Install Kit |
|---|---|
| Ford, Chevy and GMC (2011 to current), Dodge (1999 to 2012) | AIK15FD |
| GMC and Chevy (1990 to 2010) | AIK20C |
| Dodge (2013 to current) | AIK175D |
Installation usually takes under an hour with hand tools. There is no wiring, and nothing gets drilled into the factory tank.
Choosing the Right Tank
Capacity and payload
Auxiliary tanks run from 30 to 80 gallons. More capacity means fewer stops, but fuel is heavy. Diesel runs about 7 pounds per gallon, so a full 60 gallon tank adds roughly 420 pounds to the bed before you count the tank itself. Check your payload rating before sizing up.
Shape and bed space
- Rectangle: the most common. Low profile versions slide under toolboxes and tonneau covers.
- Wedge: angled body that sits tight against the bulkhead and leaves the rest of the bed open.
- L-shape: wraps over the wheel wells for more capacity in the same floor space.
- Toolbox combo: a tank and a lockable toolbox in a single unit. See fuel tank toolbox combos.
Fuel level readout
A sender with an in-cab gauge can be added to rectangle tanks when you order. It is not offered on wedge or L-shape bodies, because a float cannot read those shapes accurately. See fuel tank sending units and gauges for how that works.
Finish
Bright diamond plate aluminum or black powder coat. Powder coat is a factory finish applied before the tank ships, so it adds about a week to the build.
Common Questions
Will an auxiliary tank void my truck's warranty?
The diesel system connects through the factory fill neck and does not modify the truck's fuel system, so it does not void the truck's warranty.
Are in-bed auxiliary tanks legal?
Our auxiliary tanks meet DOT requirements for auxiliary fuel tanks, with HD aluminum construction, internal baffles, and rollover and vent protection. It is the user's responsibility to comply with local, state, and federal requirements pertaining to safe transportation, loading, and discharging of tank contents.
Can I use one auxiliary tank for both diesel and gasoline?
No. The two use completely different delivery systems, and the tanks are built for one or the other.
Can an auxiliary tank feed a generator or equipment?
A diesel auxiliary tank can be used to feed other equipment. If dispensing is your main purpose, a transfer tank with a pump is the better fit.
How fast do they ship?
Most tanks ship within 2 to 3 business days. Adding a gauge or powder coat adds about a week.
Shop In-Bed Auxiliary Fuel Tanks
Browse diesel auxiliary fuel tanks or gasoline auxiliary fuel tanks from 30 to 80 gallons, or see all auxiliary fuel tanks. Not sure which tank and kit fit your truck? Call us at (863) 261-8388 and we will match it for you.
Comparing auxiliary tanks against transfer tanks? Our Truck Bed Fuel Tank Buying Guide walks through both and helps you pick.