What's the Difference Between a Transfer Tank and an Auxiliary Tank?
If you've been shopping for extra fuel capacity for your truck, you've probably run into both terms — transfer tank and auxiliary tank. They're often used interchangeably, but they're not the same thing. Knowing the difference before you buy will make sure you end up with the right setup for what you actually need.
What is a transfer tank?
A transfer tank is a portable fuel tank that sits in your truck bed or on a trailer. It's built to dispense fuel out — to tractors, skid steers, generators, or any other equipment that needs it. A top-mounted 12V pump pulls fuel from the tank and delivers it through a hose, so you can refuel equipment right in the field without making a trip back to the pump.
Transfer tanks can carry gasoline or diesel depending on how the tank is rated. Aluminum tanks are typically approved for both, while steel tanks are generally limited to diesel and other non-flammable liquids. You can read more about fuel type rules in our post [Can I Put Gasoline in This Transfer Tank?]
Transfer tanks are the go-to choice for farmers, ranchers, contractors, and landscapers — anyone who needs to move fuel to equipment rather than extend how far their truck can go on a tank.
What is an auxiliary tank?
An auxiliary tank also sits in your truck bed, but it serves a completely different purpose. Instead of dispensing fuel to outside equipment, it connects directly to your truck's own factory fuel tank and feeds fuel into it — effectively extending your driving range without stopping at a gas station.
How it connects depends on the fuel type:
Diesel auxiliary tanks typically use a gravity feed setup. A direct line runs from the drain port of the auxiliary tank down into the truck's filler neck, letting fuel flow naturally as the main tank draws it down.
Gasoline auxiliary tanks work a little differently. Because gasoline can't gravity feed into a modern truck's emissions-controlled fuel system the same way, these tanks use a fuel pickup tube mounted in the top of the tank along with a small inline pump. That pump pushes fuel into the truck's filler neck and is controlled by a simple on/off switch inside the cab — you flip it on when you want to transfer and off when you're done.
Midway Tanks carries vehicle-specific install kits for both diesel and gasoline auxiliary setups, matched to your truck's year, make, and model so everything fits correctly from the start.
Auxiliary tanks are popular with hotshot truck drivers and people hauling campers or RVs — anyone who covers long miles and wants to bypass truck stops, take advantage of cheaper fuel prices where they find them, or simply avoid the hassle of pulling a trailer into a fuel station.
Can a tank do both?
Yes — some tanks are designed to work as both a transfer tank and an auxiliary tank. These dual-purpose setups give you the flexibility to feed your truck's factory tank when you're on the road and dispense fuel to equipment when you're on the job. If you need both capabilities, it's worth knowing that option exists rather than buying two separate tanks.
At Midway Tanks we carry dedicated transfer tanks, dedicated auxiliary tanks, and dual-purpose options. If you're not sure which configuration fits your situation, give us a call and we'll help you work through it.
Quick reference
Choose a transfer tank if you need to:
- Fuel tractors, equipment, or other vehicles in the field
- Carry extra gas or diesel to a job site
- Have a portable fuel supply on hand for multiple uses
Choose an auxiliary tank if you need to:
- Extend your truck's driving range between fuel stops
- Avoid stopping at truck stops while hauling
- Fill up where fuel is cheaper and carry it further
Consider a dual-purpose tank if you need to:
- Do both — fuel equipment in the field and extend your truck's range on the road
→ Shop Transfer Tanks at Midway Tanks