Auxiliary Fuel Tank — Built To The Truck It Is Going Into
Every stock auxiliary fuel tank in the pickup and service truck catalog is drawn to fit a generic bed dimension. Real trucks are never generic. Toolboxes, gooseneck balls, headache racks, receiver hitches, and aftermarket bed rails all change the geometry of what will fit in the bed. Ames Hydraulics fabricates auxiliary fuel tank units to the actual truck — measured on site, sized to what you actually have room for, and mounted where it belongs.
Types of Auxiliary Fuel Tank We Fabricate
In-bed diesel transfer tank
The classic. Bolts to the bed floor forward of the fifth-wheel or gooseneck ball. Sizes from 30 gallons up to 100 gallons depending on bed clearance and payload. Steel or aluminum construction, matte black or diamond-plate finish. Pump options — hand crank, 12-volt DC electric, gravity-fed nozzle.
Behind-the-cab combo toolbox and auxiliary fuel tank
Toolbox on top, auxiliary fuel tank underneath. Uses the space above the wheel wells that is often unused. Common on service trucks, oilfield trucks, and long-haul heavy-duty pickups.
Wing-tank service truck auxiliary fuel tank
Side-mounted between-the-frame-rail tanks for service body trucks. Custom shapes to work around body compartments, DEF tanks, and exhaust routing.
Underbody auxiliary fuel tank
Frame-rail mounted for heavier trucks with body space that cannot spare bed real estate. Custom fabrication because underbody clearance and mount geometry are truck-specific.
Off-highway machine auxiliary fuel tank
Auxiliary fuel tank welded or bolted to a piece of equipment — a skid steer, a track loader, a mini excavator — extending its run time between refuels. Custom mount, custom capacity, custom plumbing.
Capacities and Sizes
- 30 gallon auxiliary fuel tank — small footprint, single-cab pickups, and short-bed configurations
- 50 gallon auxiliary fuel tank — the most common size for a standard-bed diesel pickup
- 60 gallon auxiliary fuel tank — sweet spot for long-bed diesel pickups and service trucks
- 75 to 90 gallon auxiliary fuel tank — heavy service trucks, over-the-road contractors, and rural farmers
- 100 gallon auxiliary fuel tank — approaching DOT hazmat thresholds; check regulations before ordering
- Custom capacities — sized to what the truck bed can actually hold, no matter what stock catalog sizes exist
Why Custom Auxiliary Fuel Tank Beats Stock
Stock auxiliary fuel tank dimensions from the major brands assume a clear bed. The reality of most working trucks:
- A gooseneck ball or fifth-wheel hitch that eats bed length
- A cross-body toolbox behind the cab that eats bed length again
- Aftermarket bed rails that eat bed width
- A slide-in truck bed camper mount that eats floor space
- A hitch step or a bumper mount rack that eats vertical clearance
All of that shrinks the actual usable space in the bed to something less than what any stock auxiliary fuel tank was designed for. Custom fabrication solves that in one part — sized to the space, not to the catalog.
What Goes Into An Auxiliary Fuel Tank We Build
- Steel or aluminum plate cut on the shop plasma
- Full-penetration welded seams — no lap-and-tack construction
- Baffles inside the tank to prevent fuel sloshing under braking and cornering
- Sealed fill neck with lockable cap
- Filtered vent to prevent tank collapse under pump draw
- Sight gauge or electronic level sender for tank contents visibility
- Grounding stud for pump ground per DOT requirements
- Mount brackets sized to your truck’s bed floor thickness or frame rail size
- Pump mount — 12-volt DC electric pump with filter and nozzle, or hand crank for low-flow use
- Auxiliary line to the truck’s factory fuel system if a transfer-and-run setup is wanted
- DOT-legal labels and capacity stamps as required
Steel or Aluminum For The Auxiliary Fuel Tank Body?
Both are common. Steel is stronger, cheaper, and heavier — best for stationary transfer applications and off-highway machines where weight is not the issue. Aluminum is lighter, does not rust, and looks better with a diamond-plate finish — best for on-highway pickups where every pound counts against payload. Aluminum welded seams are equally as strong as steel when done properly by our shop welders certified in aluminum work.
Auxiliary Fuel Tank Regulations To Know
Under 100 gallons total capacity, a personal-use diesel auxiliary fuel tank is generally not regulated as hazmat under DOT rules. Over 100 gallons and commercial use trigger placarding and paperwork requirements. Gasoline auxiliary fuel tank installations have stricter rules than diesel because of vapor pressure. We build to the appropriate regulation for the intended use and label the tank accordingly.
Repair and Refurbish Existing Auxiliary Fuel Tank
Bent mount brackets, cracked welds at the fill neck, corroded steel tanks, and worn 12-volt pumps are all repairable. Bring the auxiliary fuel tank in for a repair quote. Often refurbishment is cheaper than replacement.
Frequently Asked Questions
What size auxiliary fuel tank fits my truck bed?
Depends on the bed length, the gooseneck or fifth-wheel setup, and any toolboxes. 50-60 gallons is typical for standard-bed pickups; long beds fit 75-100 gallons.
Steel or aluminum auxiliary fuel tank — which lasts longer?
Aluminum does not rust and lasts effectively forever with normal use. Steel lasts 15-25 years depending on how well the paint holds up and whether the tank sits in rain.
Do you install the auxiliary fuel tank in my truck?
Yes for central Iowa customers. Out-of-state customers ship the finished tank; installation is at a local shop or DIY.
Can you connect the auxiliary fuel tank to the factory fuel system?
Yes on diesel trucks — a transfer-and-run setup with a proper fuel-shutoff valve and DOT-legal plumbing. We build these regularly.
Is a 100-gallon auxiliary fuel tank legal in a pickup bed?
For diesel personal use, generally yes. Commercial use or gasoline crosses hazmat thresholds. We advise on the regulations and label per the intended use.
Related Iowa Hydraulic Repair Services
- For attachment repair and custom fabrication, see our skid steer attachments.
- For grader-blade repair and custom widths, see box blade custom fab.
- For any other custom steel or aluminum fab work, see our metal fabrication Iowa.
- For hydraulic work on service trucks and machines, see hydraulic shop near me.