Transfer Tanks vs. Auxiliary Tanks: What’s the Difference?

If you’re outfitting a work truck, hotshot rig, farm truck, or overland setup, choosing between a transfer tank and an auxiliary tank is one of the most important fuel‑system decisions you’ll make. While both increase your fuel capacity, they serve very different purposes — and ATI (Aluminum Tank Industries) builds some of the most trusted versions of each on the market.

What Is a Transfer Tank?

A transfer tank is designed to transport fuel and dispense it into equipment, machinery, generators, tractors, or other vehicles. It does not feed your truck’s factory fuel system.

✔ Key Characteristics

• Built to transport diesel from one site to another.
• Typically constructed from aluminum or steel.
• Uses a 2" NPT bung to mount a transfer pump (hand pump or 12‑volt electric).
• Includes a vent/prevent cap to allow proper airflow during pumping.
• Common sizes: 30–100 gallons.
• Can be pumped from while mounted only on private property.
• Cannot be connected to your truck’s factory fuel system.
• Not legal for gasoline in most cases unless it’s a DOT‑approved refueling tank.

✔ATI Transfer/Refueling Tank Notes

ATI’s lineup includes Refueling Tanks, which are DOT‑compliant and legal for gasoline, diesel, methanol, kerosene, aviation fuel, and more. These tanks come with dual 2" NPT bungs and are built for commercial and state applications.

 What Is an Auxiliary Tank?

An auxiliary tank is designed to extend your truck’s driving range by feeding fuel directly into your factory tank.

✔Key Characteristics

• Permanently mounted in the truck bed.
• Provides additional onboard fuel capacity for long‑distance travel or job‑site operation.
• Transfers fuel to the factory tank via:
  • Gravity feed (diesel only), or
  • Inline pump (required for gasoline).
• Keeps the factory gauge full until the auxiliary tank empties.
• Common sizes: 20–100 gallons.
• Ideal for hotshot drivers, RVers, long‑haul work trucks, and overland rigs.

✔ ATI Auxiliary Tank Notes

ATI’s AUX Series tanks are fully baffled, pressure‑tested, and built from .125" aluminum (with Severe Series at .190"). They integrate cleanly with filler‑neck kits like Fuel Shotz for seamless operation.

Why Choose ATI?

ATI is known for:

• Made‑in‑USA construction
• Thick aluminum (.125"–.190") for durability
• Full baffling for stability
• Leak/pressure testing on every tank
• Purpose‑built shapes (L‑shape, rectangle, wedge, split‑chamber)
• Tank + toolbox combos for dual‑purpose storage
• DOT‑compliant refueling options for gasoline and diesel

Their engineering and compliance standards make ATI one of the most trusted brands for both auxiliary and transfer/refueling tanks.

 Which One Should You Choose?

Choose a Transfer/Refueling Tank if you:

• Need to fuel equipment on job sites
• Work in construction, agriculture, or fleet service
• Need DOT‑approved gasoline transport (ATI Refueling Tanks)
• Want a tank + pump setup for portable fueling

Choose an Auxiliary Tank if they:

• Want to extend driving range
• Tow long distances (hotshot, RV, 5th‑wheel)
• Travel in remote areas with limited fuel access
• Want a set‑and‑forget system that keeps the factory gauge full