50 Gallon Fuel Transfer Tank: What It Is, How It Works, and What to Know Before You Buy

A 50 gallon fuel transfer tank is a portable, secondary fuel storage container mounted in the bed of a pickup truck or trailer. It lets drivers carry a significant reserve of diesel or gasoline — without stopping at a pump. For operators working in remote areas, on farms, at job sites, or hauling equipment across long stretches of highway, that extra range can be the difference between a productive day and a costly delay.

What a Fuel Transfer Tank Actually Does

A transfer tank stores fuel on board the vehicle and delivers it — either by gravity feed or with an onboard 12V pump — directly into the truck's main fuel tank or into equipment in the field. The tank sits in the truck bed and is secured to the bed floor or rail system with tie-downs or mounting brackets.

Most 50 gallon transfer tanks are made from either aluminum or steel, each with trade-offs:

Material	Weight	Rust Resistance	Cost
Aluminum	Lighter	Excellent	Higher
Steel	Heavier	Prone to rust if uncoated	Lower

A 50 gallon capacity is a common middle-ground size — large enough to meaningfully extend range or service equipment, but still manageable in a standard short or long bed truck. When full, diesel weighs roughly 7 pounds per gallon, so a full 50 gallon diesel tank adds approximately 350 pounds to the truck bed. Gasoline is slightly lighter at around 6.3 pounds per gallon, adding roughly 315 pounds at capacity.

That payload impact matters. Every pickup has a payload rating — the maximum combined weight of passengers, cargo, and anything in the bed. A full transfer tank can consume a significant portion of that rating, especially on half-ton trucks.

How the Transfer System Works

Most 50 gallon tanks include or are compatible with a 12-volt DC fuel transfer pump, a nozzle, and a hose. You run the pump from the truck's battery — either hardwired or connected via alligator clips to a portable power source — and fuel moves from the transfer tank into whatever you're filling.

Some setups use gravity feed if the tank is mounted high enough and the destination tank is lower, but pump-driven systems are more common and more controllable.

Key components to understand:

Pump flow rate — measured in gallons per minute (GPM); a typical 12V pump for this size tank moves 8–15 GPM
Venting — tanks need a vent to prevent vacuum lock and pressure buildup
Fuel compatibility — tanks are typically rated for diesel, gasoline, or both; check manufacturer specs before using
Lockable access — most tanks include a lockable fill cap or compartment to prevent theft or tampering

Regulations and Legal Considerations ⚠️

This is where things vary significantly by location, vehicle type, and use case.

Federal DOT regulations govern the transport of flammable liquids on public roads. A tank used to transport fuel — not just store it on a private property — may be subject to hazardous materials rules depending on the quantity, the type of fuel, and whether it's for personal or commercial use. DOT-approved tanks meet specific standards for venting, pressure, and construction.

State rules add another layer. Some states have additional requirements around:

Whether the tank must be DOT-certified for road use
Permit requirements for commercial fuel transport
Whether fuel transported this way is subject to state fuel tax reporting
Inspection or mounting requirements

If you're a private individual using a transfer tank on your own ranch or property and never driving it on public roads, the rules are different from a commercial contractor transporting diesel across state lines. The amount of fuel also matters — thresholds that trigger stricter DOT requirements vary.

Mounting requirements matter too. A 50 gallon tank full of diesel weighs several hundred pounds. If it's not properly secured and it shifts or comes loose in an accident or hard stop, it's a serious safety hazard. How you mount it — and what that requires — depends on your truck bed, the tank's design, and applicable regulations.

Variables That Shape How This Works for Any Given Owner

No two setups are identical. The factors that change the math include:

Truck payload capacity — a three-quarter-ton or one-ton truck handles this payload differently than a half-ton
Intended use — farm or off-road use only vs. regular highway driving changes what regulations apply
Fuel type — diesel and gasoline transfer tanks aren't always interchangeable; some are rated for both, some aren't
Pump requirements — some applications (equipment fueling, faster fill times) need higher GPM ratings
Cab or bed configuration — long beds accommodate larger or dual tanks more easily than short beds
State and jurisdiction — local fuel transport rules and tax requirements vary

What "50 Gallon" Looks Like in Practice 🚛

At highway fuel economy, a typical diesel pickup might travel 15–20 miles per gallon under light load. An additional 50 gallons theoretically adds 750–1,000 miles of range — but that figure drops when the truck is already hauling heavy cargo or towing. The real-world benefit is less about emergency range and more about avoiding pump stops in remote areas, fueling equipment without a separate fuel run, or reducing downtime on a job site.