What Type of Fuel Tank Do I Need?

"Transfer Tank", "Refueling Tank", "Auxiliary Tank" or "Transfer/Auxiliary Tank" all sound like they do the same thing but they are different. And, while there are companies like Titan Fuel Tanks that make extra capacity tanks made to replace your factory tank or mount in place of a spare tire.

The tanks we are discussing here typically mount in the bed of your truck.

These tanks are not vehicle specific so bed size and bed configuration are more important than whether you're driving a Ford, Chevy, Dodge or GMC Truck. Measuring the area you are planning to mount your tank, carefully, is absolutely the first step.

Let's Talk Tank Differences First

The "Transfer" tank is typically made to move fuel from one vehicle to another or to a piece of equipment. Unless the manufacturer specifically states that it may be used to transfer Flammable Fuels like gasoline or aviation fuel they are to be used only for non-flammable fuels like diesel. They can only be used to transfer fuel from your vehicle to another vehicle or equipment on Private Property if they are not DOT certified. Most CANNOT be connected to your vehicle's fuel system. Transfer Tanks have 2 bungs, one for a tank mounted pump and one for the filler and cap. While all tanks are subject to federal, state and local laws, transfer tanks carrying flammable liquids like gasoline often have their own set of laws and are illegal in and cannot be sold, at all, in some states like California.

Transfer tanks require a pump, like the high-quality offerings from GPI, are usually sold separately,

An "Auxiliary Tank” can be connected to your vehicles fuel system extending your range for fewer refueling stops. Diesel auxiliary kits are the easiest and simplest to install and many manufacturers make, inexpensive gravity feed kits, from ATI and RDS, for diesel applications.


On Diesel applications, fuel can be drawn from a port at the bottom of the tank and fed into the vehicle's factory fuel fill tube. As long as the cap is secured tightly there will be no overflow. Some Auxiliary tanks can be used as transfer tanks, as long as they have a bung for mounting the pump and one for the fill. While there are some gasoline auxiliary tanks available, installation is much more complicated and they are illegal in some jurisdictions. Gasoline AUX Tanks must have the fuel drawn from the top of the tank via a switch controlled electric pump. The tank must have a vent and that vent needs to be plumbed into the vehicle's factory closed fuel evaporative control system. If not properly plumbed, flammable vapors will be released polluting the air and posing a fire risk. Improperly vented gasoline AUX tanks will trigger "Check Engine Warning" light. Local laws and professional installation should be researched before you purchase a gasoline auxiliary tank. Also, a gasoline tank legal in one jurisdiction may be illegal in another so consider your route and destination if your planning long trips.

A "Refueling Tank" is, technically, a transfer tank but some manufacturers use that term when referring to a DOT Certified so it can be used for commerce and on public roadways, for example, a roadside service truck that is equipped to assist drivers who have "run out of gas" and are stranded on the side of a public highway. These tanks can be for flammable and non-flammable fuels. Refueling tanks also work well with mobile equipment like gasoline-powered generators, pumps etc. Refueling tanks cannot be connected to your existing fuel system and used as an auxiliary tank. Again, State and local laws should be researched before purchasing.

Each tank manufacturer offers unique shapes and configurations, there are 'L' shaped, square, rectangular, low profile, wedge, and slim and tall configurations. There are even tanks that can carry two different types of fuel like gasoline and diesel in the same tank. What one manufacturer doesn't have the other may have. Tanks can be made of aluminum, steel or poly and finished in a natural finish or powder coated.

If you need a little more utility most manufacturers have tanks that can be combined with a toolbox.

So, once you have decided on the type of tank, we need to find the perfect fit. Carefully measuring your truck bed is critical. Use our guide "Measuring for A Bed Mounted Transfer or Auxiliary Tank". Bed width, side rail height and distance from the bulkhead to the beginning of the wheel well, measured on the bed floor, are critical measurements when choosing a tank.

If the tank you are considering is going to rise above the bed rail you need to compare floor measurement to top rail measurements in case there is a contour, top or bottom. Be mindful that any style tank will not rest flush against the truck bed's bulkhead (end of the bed closest to the cab). At least a few inches is necessary for access to the shut-off valve or tank drain fitting. The measurements listed for all tanks do not include mounting tabs, which typically add 1.5"-3" and the height of the filler which is about 2.5"-3". Also, depending on the style to be used, a transfer pump will sit 8"-10" above the tank.

Above all, safe and legal installation should be your highest priority with a tank purchase. Please feel free to contact us with any questions.

Please contact us if you have any questions regarding the type of Fuel Tank that is right for you. 889-590-4769

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