Running low on diesel or gasoline during long hauls or on remote job sites wastes time and interrupts your work. Picking the wrong auxiliary fuel tank for truck bed setups can also block your fifth-wheel hitch, exceed payload limits, or fail state transport rules.
This guide compares 10 rectangular, L-shape, and toolbox combo tanks to help you find the right capacity and dimensions for your pickup. We built this list by comparing retailer listings, manufacturer specifications, and verified buyer feedback. Confirm current price and exact vehicle fitment on the retailer page before ordering.
How to choose an auxiliary fuel tank for truck bed setups
Choosing an auxiliary fuel tank for truck bed use requires matching the tank dimensions to your pickup bed width, picking between gravity-feed or pump setups, and verifying federal fuel transport rules. Check your available payload capacity and tonneau cover clearance before ordering any tank.
Bed fitment and clearance: Measure the width between your wheel wells and the height under your bed rails or tonneau cover. Standard full-size beds fit 50-inch to 60-inch wide tanks, while midsize trucks need compact footprints.
Tank shape and style: Rectangular tanks take up a flat footprint at the front of the bed. L-shape tanks wrap under an existing crossover toolbox, and combo units merge a locked tool chest with liquid storage in one aluminum frame.
Fuel type and plumbing rules: Diesel fuel can feed directly into your factory tank using a Department of Transportation compliant gravity-feed kit. Gasoline requires a dedicated 12-volt or manual transfer pump to move fuel safely.
Capacity and loaded weight: Diesel weighs about 7.1 pounds per gallon, and gasoline weighs about 6.3 pounds per gallon. A full 50-gallon aluminum tank adds over 400 pounds to your truck bed, which reduces your remaining payload and towing limits.
Internal baffles and security: Built-in aluminum baffles reduce liquid sloshing when you brake or turn on the highway. If you park at public job sites, look for combo models with stainless steel locking paddle latches and reinforced lids.
RDS MFG INC 71083 Rectangular Auxiliary/Transfer Fuel Tank – 45 Gallon Capacity
RDS MFG INC · 57″ L × 9.5″ W × 20″ H · Bright diamond-tread aluminum
Quick Answer
The RDS MFG INC 71083 rectangular tank earns our top spot by packing 45 gallons of DOT-approved fuel storage into a slim 9.5-inch-deep footprint that preserves almost your entire pickup bed floor.
Built from 0.125-inch heavy-duty diamond-tread aluminum, this vertical tank mounts flush against your cab wall using welded 3/16-inch side brackets. Internal baffles reduce liquid sloshing on the highway, while a 2-inch female pipe thread coupling accepts a manual or 12-volt transfer pump for refueling equipment or feeding diesel into your factory tank.
Pros
- Slim 9.5-inch depth leaves maximum flat bed space for fifth-wheel hitches or cargo
- 100% pressure-tested, fully welded 0.125-inch aluminum seams will never rust
- DOT-approved for diesel, gasoline, and aviation fuel transport
- Built-in internal baffles, rollover safety valve, and locking fill cap come standard
Cons
- Transfer pump and diesel gravity-feed plumbing kit (RDS 011025) are sold separately
- Mounting tabs add 1 inch to each side (59 inches total width needed for floor bolts)
- Fill cap adds 2.5 inches to the 20-inch tank height, which can block low-profile tonneau covers
Skip it if: you want integrated locked tool storage in the same footprint, or need a low-profile tank that sits completely under a flush-mount tonneau cover.
TTL Transfer Refueling Tank – Gas or Diesel Fuel | 95 Gallon Capacity
Aluminum Tank Industries (ATI) · 48.5″ L × 33″ W × 26″ H · Bright diamond-plate aluminum
Quick Answer
The TTL Transfer Refueling Tank TTL95 is an L-shaped aluminum tank rated for 95 gallons of gasoline, diesel, kerosene, methanol, or aviation fuel. It slides under most crossover truck toolboxes to pair high liquid volume with bed storage.
Aluminum Tank Industries builds this unit from 0.125-inch diamond-plate aluminum with full internal baffles. Two 2-inch NPT reinforced bungs let you mount the fill cap and pump on either side. Every tank undergoes a factory pressure and leak test.
Pros
- Carries a U.S. DOT special permit for gasoline, diesel, methanol, kerosene, and aviation fuel
- L-shaped profile fits beneath standard crossover toolboxes or installs in reverse for easier removal
- Dual 2-inch NPT reinforced bungs allow driver-side or passenger-side pump mounting
- Includes internal baffles, a commercial lockable vent filler cap, and a 3/8-inch NPT drain plug
Cons
- The maker states that standard 0.125-inch tanks support transfer pumps up to 30 lbs only
- A full 95-gallon load adds over 670 lbs of fuel weight on top of the 97-lb empty tank
- Transfer pump, hoses, and mounting bolt hardware are sold separately on retailer listings
Skip it if: you drive a half-ton pickup with limited payload capacity, or plan to mount a commercial transfer pump over 30 lbs.
Dee Zee Auxiliary Diesel Fuel Transfer Tank | 43 Gallon Capacity
Dee Zee · 54″ L × 18″ W × 16″ H · Black Brite-Tread aluminum
Quick Answer
The Dee Zee Auxiliary Diesel Fuel Transfer Tank DZ92740XB pairs a 43-gallon black aluminum tank with a bolted utility chest in a low 16-inch profile. The manufacturer states that its radius curve design eliminates key weld pressure points.
Constructed from heavy-gauge Brite-Tread aluminum with a black powder coat finish, this unit mounts to the front of your pickup bed floor. Retailer listings note internal stability baffles, a 0.375-inch drainage plug, a lockable cap, and a venting coupler for diesel transfer.
Pros
- Low 16-inch height and 54-inch length fit 6.5-foot half-ton and heavy-duty pickup beds
- Bolted utility chest adds lockable tool storage with dampened gas shocks and a removable tray
- Radius curve aluminum construction removes key weld stress points along the tank body
- Includes internal stability baffles, dual threaded bungs, a venting coupler, and a 0.375-inch drain plug
Cons
- The manufacturer states it will not fit 5-foot short bed truck models
- Rated for diesel fuel only and is not approved for gasoline or commercial Title 49 transport
- Diesel fuel line connection kits (such as Dee Zee DZ97960) and transfer pumps are sold separately
Skip it if: you drive a pickup with a 5-foot short bed, or need a tank certified for hauling gasoline.
RDS Aluminum Auxiliary Fuel Tank Toolbox Combo | 60 Gallon Capacity
RDS MFG INC · 55″ L × 20″ W × 19″ H · Black diamond-plate aluminum
Quick Answer
The RDS Aluminum Auxiliary Fuel Tank Toolbox Combo 72743PC houses a 60-gallon rectangular fuel tank and a 48-inch top tool chest inside a 55-inch footprint. Its enclosed fuel filler shroud locks under the toolbox lid to prevent tampering.
Built from black powder-coated diamond-plate aluminum, this combo unit measures 55 inches long by 20 inches wide by 19 inches high. Retailer listings state that it includes internal baffles, a manual sight gauge, a 3/8-inch drain fitting, and dual gas cylinders to prop the crowned lid open.
Pros
- Recessed fuel filler shroud secures the fill neck and manual sight gauge behind a linked stainless steel lock
- 60-gallon capacity and 19-inch height sit flush with standard full-size pickup bed rails
- Internal aluminum baffles reduce liquid sloshing while towing or braking
- Includes a 2-inch inlet port, a 3/8-inch FPT bottom outlet port, and mounting hardware
Cons
- Fuel filler shroud reduces the upper toolbox width from 55 inches down to 48 inches
- Shallow 6.25-inch toolbox depth holds hand tools and straps rather than bulky power tools
- Gravity-feed diesel plumbing kits and electric transfer pumps are sold separately
Skip it if: you need a full-width 55-inch tool chest for tall power tools, or want a transfer tank with a pre-installed 12-volt pump.
RDS MFG INC – 72744 Fuel Tank Toolbox Combo | 60 Gallon Capacity
RDS MFG INC · 55″ L × 20″ W × 22.75″ H · Bright diamond-plate aluminum
Quick Answer
The RDS MFG INC – 72744 Fuel Tank Toolbox Combo pairs a 60-gallon rectangular fuel tank with a 10-inch-deep upper tool chest. Its 22.75-inch overall height gives you 3.75 inches more vertical tool storage than standard 19-inch combo units.
RDS builds the lower tank from 0.125-inch bright diamond-plate aluminum and the upper toolbox from 0.058-inch aluminum. Retailer listings state that an enclosed fuel filler shroud sits under the crowned lid so one linked stainless steel paddle lock secures both your tools and the 2-inch fill neck.
Pros
- 10-inch-deep upper toolbox holds taller hand tools and recovery gear than 6.25-inch low-profile chests
- Recessed fuel filler shroud locks the 2-inch fill cap and manual sight gauge beneath the reinforced toolbox lid
- 100% pressure-tested and submerged 0.125-inch aluminum tank includes internal baffles to reduce sloshing
- Two gas-filled lift cylinders prop the lid open while linked stainless steel paddle handles open from either side
Cons
- Tall 22.75-inch height rises above standard pickup bed rails and blocks over-the-rail tonneau covers
- Bottom mounting tabs add 1 inch to the 20-inch box width (requiring 21 inches of floor clearance)
- Diesel gravity-feed installation kits and transfer pumps are sold separately
Skip it if: you need a flush 19-inch tank that sits below your pickup bed rails, or want a full 55-inch-wide tool compartment without an internal filler shroud.
RDS Manufacturing 72748 Fuel Tank Combo | 90 Gallon Capacity
RDS MFG INC · 55″ L × 30″ W × 22.25″ H · Bright diamond-plate aluminum
Quick Answer
The RDS Manufacturing 72748 Fuel Tank Combo is rated for 91 gallons of fuel storage under a 48-inch by 30-inch by 9-inch upper toolbox. Its 30-inch front-to-back depth provides high liquid volume for 8-foot pickup beds.
The manufacturer builds the lower tank from 0.125-inch diamond-plate aluminum and the upper chest from 0.058-inch aluminum. Retailer listings state that an enclosed fuel filler shroud locks the fill cap, suction tube, and manual sight gauge beneath the reinforced lid.
Pros
- 91-gallon rated capacity extends driving range for long-bed heavy-duty work trucks
- 30-inch-deep upper toolbox (48″ L × 30″ W × 9″ H) stores wider gear than 20-inch combo chests
- Recessed fuel filler shroud secures the gas cap and manual sight gauge under linked stainless steel key locks
- Includes internal aluminum baffles, a suction tube, return and drain fittings, and fully welded seams
Cons
- 30-inch front-to-back width takes up 10 inches more bed floor length than 60-gallon models
- 170-lb empty weight plus 91 gallons of diesel adds over 815 lbs to your pickup bed
- Diesel gravity-feed plumbing kits and electric transfer pumps are sold separately
Skip it if: you drive a short-bed truck where a 30-inch-deep box blocks your fifth-wheel hitch, or need to keep payload weight low.
Dee Zee DZ92740B Combo Transfer Tank & Tool Box | 40 Gallon Capacity
Dee Zee · 54″ L × 18″ W × 16″ H · Black Brite-Tread aluminum
Quick Answer
The Dee Zee DZ92740B Combo Transfer Tank & Tool Box pairs a 43-gallon rated liquid transfer tank (40-gallon class) with a bolted utility chest inside a low 16-inch profile. The manufacturer states this low height clears most pickup tonneau covers.
Dee Zee builds the tank from 0.125-inch Brite-Tread aluminum and the upper chest from 0.056-inch aluminum with a black powder coat finish. Retailer listings state that three internal stability baffles, a lockable cap, a 0.375-inch drain plug, and a venting coupler come standard.
Pros
- Low 16-inch overall height sits below standard pickup bed rails to fit under most tonneau covers
- Radius curve 0.125-inch aluminum body removes weld pressure points along the tank walls
- Bolted 0.056-inch aluminum utility chest features dampened gas shocks and lockable stainless steel paddle handles
- Includes three internal stability baffles, a lockable fill cap, a venting coupler, and a 0.375-inch drainage plug
Cons
- The manufacturer states this non-auxiliary transfer model is for private use with non-flammable liquids and does not meet Title 49 commercial transport rules
- Bolted utility chest measures 7 inches high by 11.5 inches deep, which limits storage to small hand tools
- Transfer pumps, hoses, and mounting bolts are sold separately
Skip it if: you need a DOT-approved tank for commercial highway fuel transport, or want a direct gravity-feed auxiliary diesel system (see the DZ92740XB instead).
RDS 71789 Rectangular Auxiliary/Transfer Combo Fuel Tank | 51 Gallon Capacity
RDS MFG INC · 50″ L × 20″ W × 19″ H · Machined aluminum finish
Quick Answer
The RDS 71789 Rectangular Auxiliary/Transfer Combo Fuel Tank combines a 51-gallon fuel storage vessel with an integrated tool chest inside a compact 50-inch bed footprint.
Manufactured from heavy-duty aluminum plates, this unit features dual stainless steel paddle handles and a mounting kit. Retailer listings highlight its rectangular configuration designed for balanced fluid transport and secure gear storage.
Pros
- 51-gallon capacity extends driving range for long trips and remote job sites
- Dual stainless steel paddle handles offer secure, corrosion-resistant latching
- Includes a mounting kit for straightforward bed anchoring
- Integrated tool chest section consolidates liquid hauling and gear storage
Cons
- Some Amazon buyer feedback notes packaging wear and minor transit dents upon delivery
- 88-lb empty weight requires assistance during lifting and positioning
- Transfer pumps and vehicle-specific plumbing kits are sold separately
Skip it if: you need a lightweight standalone transfer tank without built-in tool storage, or have a tight delivery timeline where shipping wear is a concern.
RDS Fuel Transfer and Auxiliary Toolbox Combo | 60 Gallon Capacity
RDS MFG INC · 55″ L × 20″ W × 19″ H · Bright diamond-plate aluminum
Quick Answer
The RDS Fuel Transfer and Auxiliary Toolbox Combo integrates a 60-gallon liquid storage tank with a locking top tool chest inside a 55-inch bright diamond-plate aluminum frame.
Manufactured with fully welded seams and internal baffles, this combo unit handles heavy-duty field transport while keeping gear secure under dual paddle latches. Retailer listings note that it includes mounting brackets and a recessed filler neck.
Pros
- 60-gallon capacity extends your driving and equipment fueling range significantly
- Locking paddle handles protect valuable tools and equipment from theft at job sites
- Internal aluminum baffles reduce dangerous fluid sloshing during transit
- Bright diamond-plate aluminum construction resists rust and harsh weather
Cons
- 96-lb empty weight requires multiple people to safely position in the truck bed
- Transfer pumps and vehicle plumbing kits must be purchased separately
- Combo housing takes up substantial bed floor space compared to slim standalone tanks
Skip it if: you prefer a lightweight standalone tank without built-in tool storage, or drive a compact truck with limited bed width.
RDS MFG INC 72548 Fuel Transfer Tank/Auxiliary Fuel Tank | 60 Gallon Capacity
RDS MFG INC · 60-Gallon Capacity · Heavy-duty aluminum
Quick Answer
The RDS MFG INC 72548 Fuel Transfer Tank/Auxiliary Fuel Tank provides 60 gallons of heavy-duty liquid storage in a rugged rectangular aluminum vessel built for commercial and farm transport.
Constructed with fully welded seams and internal baffles, this tank secures fluid loads during transport. Retailer listings and buyer feedback note its reliable dual-purpose design for auxiliary diesel feed or manual pump transfer.
Pros
- 60-gallon capacity extends refueling intervals for work trucks and heavy machinery
- Fully welded heavy-duty aluminum construction resists rust and environmental wear
- Internal stability baffles reduce liquid sloshing while driving on uneven terrain
- Configured for both standalone fluid transfer and auxiliary diesel feed
Cons
- Large 60-gallon footprint takes up substantial space in your pickup bed
- Transfer pumps, hoses, and plumbing kits are sold separately
- Heavy empty weight requires assistance during initial truck bed placement
Skip it if: you need integrated tool storage in the same unit, or drive a compact truck with limited bed floor space.
FAQ’s
Are auxiliary fuel tanks legal for highway use?
Auxiliary fuel tanks built to Department of Transportation standards are legal for highway use when installed correctly. Buyers must check federal and state laws regarding fuel type and gravity-feed configurations. Gasoline typically requires active pump systems rather than simple gravity feeds.
Can I connect an auxiliary tank directly to my factory fuel line?
Connecting an auxiliary tank to your factory fuel system requires a certified diesel installation kit. Most manufacturers sell these plumbing kits separately. Gasoline tanks cannot use standard gravity-feed kits due to safety regulations.
Do transfer tanks come with a fuel pump?
Most standalone transfer tanks ship without a fuel pump. Users must purchase a manual or 12-volt electric transfer pump separately. Combo units sometimes include pump mounting provisions on the toolbox lid.
How do internal baffles help during transport?
Internal baffles divide the tank interior to restrict fluid movement. This structural feature reduces dangerous liquid sloshing while braking or turning. Baffles also provide added structural strength to the aluminum walls.
What maintenance do aluminum transfer tanks require?
Aluminum tanks require minimal maintenance because the metal does not rust. Owners should inspect rubber seals, drain plugs, and mounting brackets annually. Checking fuel caps and rollover valves ensures proper venting.
Will a toolbox combo tank fit under a tonneau cover?
Standard fuel tank and toolbox combos usually sit flush with bed rails and block traditional covers. Specialized low-profile models exist for specific tonneau configurations. Buyers must measure vertical clearance carefully before ordering.
Conclusion
Choosing the right auxiliary fuel tank requires carefully matching your pickup bed dimensions, hauling capacity limits, and equipment storage needs. Reviewing all of these rectangular, L-shape, and toolbox combo options helps you find a reliable fuel hauling setup.
If you need a slim tank that preserves flat bed space, look at the RDS 71083 rectangular model. If you want massive fluid storage for commercial chassis transport, look at the TTL 95-gallon L-shape tank. If you require integrated gear storage with lower fluid volume, look at the Dee Zee 43-gallon utility combo. If you need 60-gallon capacity with an upper tool chest, look at the RDS 60-gallon toolbox combos.