What's the Difference?
If you've spent any time shopping for a truck-bed fuel tank, you've probably run into two terms that get used almost interchangeably: transfer tank and auxiliary tank. They look similar, they both live in your truck bed, and they both hold fuel. However, they're built for two different jobs.
Buying the wrong tank type can mean DOT compliance headaches, the wrong pump setup, or a tank that doesn't actually solve the problem you bought it for. Here's how to tell them apart and figure out which one belongs on your truck.
What Is a Transfer Tank?
A transfer tank is designed to move fuel from Point A to Point B, not to feed your truck's own engine. Think of it as a mobile fuel station you carry with you. Transfer tanks are built to dispense fuel out of the tank into other equipment: generators, tractors, mowers, or a fleet of vehicles or equipment.
Because they're meant for dispensing, transfer tanks are almost always paired with a transfer tank pump and hose/nozzle setup so you can fill other equipment on the spot. You'll find these on:
- Construction and job site crews fueling heavy equipment like excavators and skid steers.
- Farms and ranches refueling tractors, combines, irrigation systems, ATVs in the field.
- Fleet operations that top off service trucks and maintenance vehicles on location
What Is an Auxiliary Tank?
An auxiliary tank has a different purpose: it extends the fuel range of the truck it's mounted on. Rather than dispensing fuel to other equipment, an auxiliary tank typically feeds directly into (or supplements) your truck's own fuel system, letting you drive farther between fill-ups.
Auxiliary tanks are popular with:
- Long-haul drivers and truckers who want fewer fuel stops
- RV and towing setups covering long distances
- Anyone working in remote areas where fuel stations are few and far between
Transfer Tank vs. Auxiliary Tank: Key Differences
| Transfer Tank | Auxiliary Tank | |
|---|---|---|
| Primary purpose | Dispense fuel to other equipment | Extend your truck's own fuel range |
| Fuel flow | Out to external equipment (via pump) | Feeds into your vehicle's fuel system |
| Typical add-on | Transfer pump, hose, nozzle | Fuel line kit, sometimes a separate fill point |
| Best for | Jobsites, farms, fleets refueling other machines | Long-distance driving, remote work, towing |
| DOT/legal notes | Subject to regulations if hauling fuel for resale or across state lines (check local/DOT rules) | Subject to regulations around fuel system modifications (check vehicle and state requirements) |
A quick way to remember it: transfer tanks fuel other things; auxiliary tanks fuel your truck.
Do You Need a Pump?
This is one of the biggest points of confusion. Transfer tanks generally require a transfer tank pump to actually dispense fuel, the tank itself is just storage. Auxiliary tank setups vary by system. Some integrate directly with your factory fuel line, while others use a transfer pump to move fuel into your main tank as needed. Always check the specific tank's fitment and plumbing requirements before you buy, and don't forget pump accessories like hoses, nozzles, and filters if you're setting up a full dispensing system.
Which One Do You Actually Need?
Ask yourself these questions:
- Am I fueling equipment other than my truck? → You want a transfer tank.
- Am I just trying to go farther between fill-ups? → You want an auxiliary tank.
- Need two types of fuel? → You want a split tank.
- Am I tight on bed space but still need storage? → Consider a tank/box combo, which pairs a tank with a toolbox in one unit.
Find the Right Tank for Your Truck
Whether you need to keep equipment running on a remote job site or want to cut down on fuel stops during long hauls, Elite Truck carries hundreds of DOT-approved transfer tanks, auxiliary tanks, tank/box combos, all from industry-leading brands and all backed by the Elite Promise.
Not sure which setup fits your truck?
Elite Truck was founded by a diesel mechanic, and that heritage has helped the Elite Truck team excel in tank product support.