After researching manufacturer specifications, industry safety standards, and aggregated owner feedback, we evaluated the top auxiliary fuel tanks for diesel trucks. Our comparison focuses on capacity, material, installation complexity, and real-world durability. While many tanks promise extended range, we found that not all deliver on fitment or leak prevention. Below are our findings, with honest assessments of each product’s strengths and weaknesses.
| Photo | Product | Score | Buy |
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Transfer Flow 50 Gallon Replacement Fuel Tank Best Overall 50 gallon capacity, diamond-plate aluminum, replaces factory tank |
9.2 | 🛒 Check Price |
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RDS Manufacturing Aluminum 60 Gallon Transfer Tank Best Value 60 gallon capacity, diamond-plate aluminum, bed-mounted |
8.7 | 🛒 Check Price |
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Titan Fuel Tanks 30 Gallon Auxiliary Tank Best Compact 30 gallon capacity, polyethylene, under-bed or bed mount |
8.4 | 🛒 Check Price |
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Northern Tool + Equipment 55 Gallon Diesel Fuel Tank Budget Pick 55 gallon capacity, steel, skid-mounted |
7.8 | 🛒 Check Price |
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Better Built 50 Gallon Oval Fuel Tank Editor's Choice 50 gallon capacity, steel, oval shape for bed fit |
8.1 | 🛒 Check Price |
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LRA 40 Gallon Long Range Fuel Tank Premium Pick 40 gallon capacity, aluminum, replacement tank for Ford Super Duty |
9.0 | 🛒 Check Price |
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Scepter 20 Gallon Military-Style Fuel Can Portable Option 20 gallon capacity, high-density polyethylene, jerry can style |
7.3 | 🛒 Check Price |
1. Transfer Flow 50 Gallon Replacement Fuel Tank: Best Overall
In our evaluation, the Transfer Flow 50 gallon replacement tank stands out for its seamless integration and robust build. It replaces the stock tank entirely, offering a net gain of 30-40 gallons depending on the original capacity. Owner feedback consistently highlights the high-quality welds and the included sending unit that works with factory gauges. However, installation is not a DIY job for most; it requires dropping the factory tank and potentially adapting fuel lines. We recommend this for owners who want a permanent, bed-space-free solution and are willing to invest in professional installation.
Who should skip it: If you need a temporary or tool-free setup, or if you have a short-bed truck where clearance is tight, this tank may not fit. Also, the higher initial investment might not suit budget-conscious shoppers.
- Direct replacement for factory tank, no loss of bed space
- Constructed from 5052 aluminum alloy with internal baffles
- Includes sender unit, vent, and all necessary hardware
Pros: Maximizes range without sacrificing cargo area; Rust-proof aluminum construction with 5-year warranty
Cons: Professional installation recommended, may require modifications
2. RDS Manufacturing Aluminum 60 Gallon Transfer Tank: Best Value
Based on owner feedback and the spec sheets, the RDS 60 gallon tank offers the best balance of price and capacity. It is bed-mounted, so installation is straightforward with basic tools. The diamond-plate aluminum resists dents and rust, and the included ball valve and lockable cap add convenience. Many users report that it fits well in full-size trucks without interfering with tonneau covers. However, when full, it adds over 400 pounds and occupies valuable bed space.
Who should skip it: If you regularly need your entire bed for hauling cargo, or if you have a short bed that already feels cramped, this tank may be too intrusive. Also, the lack of internal baffles can cause fuel slosh if not completely full.
- 60 gallon capacity with 12 gauge aluminum diamond plate
- Includes ball valve, fill neck, and lockable cap
- Meets DOT and CARB requirements for diesel storage
Pros: Excellent value per gallon of capacity; Durable construction with corrosion-resistant coating
Cons: Takes up significant bed space when full
3. Titan Fuel Tanks 30 Gallon Auxiliary Tank: Best Compact
In our comparison, the Titan 30 gallon tank is a solid choice for those who need moderate extra range without a huge weight penalty. Its rotomolded polyethylene construction is lighter than aluminum and won’t rust, but some owners report slight warping in extreme heat. The included installation kit is comprehensive, making it a good DIY option. It is also available in under-bed configurations for trucks with space, preserving bed room.
Who should skip it: If you want the maximum durability of metal, or if you plan to store diesel for long periods (polyethylene can be slightly porous to hydrocarbons), consider an aluminum tank instead. Also, the 30 gallon capacity may not satisfy long-haul drivers.
- Rotomolded polyethylene for impact and corrosion resistance
- Can be mounted under the vehicle or in the bed
- Includes fuel pick-up and return line kit
Pros: Lightweight and easy to install with included brackets; Versatile mounting options fit many truck models
Cons: Polyethylene can expand with heat, affecting fit over time
4. Northern Tool + Equipment 55 Gallon Diesel Fuel Tank: Budget Pick
Based on owner feedback, the Northern Tool 55 gallon tank is a budget-friendly option for stationary or job-site use. It is not designed for permanent truck mounting but can be strapped in the bed. The steel construction is durable but prone to rust if scratched. The included hand pump works, but many users upgrade to a 12V pump for convenience. It meets basic safety standards, but lacks internal baffles.
Who should skip it: If you need a permanent, weather-resistant installation for an on-road truck, this tank is not ideal. Also, if you plan to transfer fuel frequently, invest in a pump upgrade.
- 55 gallon capacity with heavy-duty steel construction
- Skid base for forklift or pallet jack transport
- Includes hand pump and 12-foot hose
Pros: Lowest cost per gallon among large tanks; Portable skid design for job sites
Cons: Steel can rust if not kept painted or in dry conditions; Hand pump is slow and not suitable for frequent use
5. Better Built 50 Gallon Oval Fuel Tank: Editor's Choice
We researched the Better Built 50 gallon oval tank and found it to be a practical choice for trucks with limited bed height. The oval shape allows it to sit lower, improving center of gravity. The powder coating helps resist rust, but owner feedback indicates that chips can lead to corrosion over time. Installation is moderate, with clear instructions. However, a few users noted weld leaks, so inspect upon arrival.
Who should skip it: If you are concerned about weight or want a tank that will never rust, look at aluminum. Also, if you need a tank that can handle off-road abuse, the steel may dent more easily than aluminum.
- Oval profile maximizes bed space and clearance
- Powder-coated steel with drain plug and fill cap
- Includes mounting brackets and hose kit
Pros: Oval shape fits well in truck beds with toolboxes; Solid steel construction with good corrosion resistance
Cons: Heavier than aluminum or polyethylene alternatives; Some units reported poor weld quality at seams
6. LRA 40 Gallon Long Range Fuel Tank: Premium Pick
Our evaluation of the LRA 40 gallon tank reveals a purpose-built solution for Ford Super Duty owners. It is a direct replacement, offering a clean installation that looks OEM. The TIG-welded aluminum is top-notch, and the internal sump ensures consistent fuel pickup even at low levels. Owner feedback praises the improved range and the fact that it uses the factory fuel gauge. However, it is expensive and limited to compatible trucks.
Who should skip it: If you do not drive a Ford Super Duty (1999-2007 or 2011+ depending on model), this tank will not fit. Also, if you need a larger capacity than 40 gallons, other options may be better.
- Replaces factory tank on Ford Super Duty (specific years)
- TIG-welded aluminum with internal baffles and sump
- Includes sending unit, harness, and detailed instructions
Pros: Factory fit and finish with no bed intrusion; High-quality welds and excellent fuel pickup design
Cons: Only fits specific Ford models, not universal; Premium price compared to universal tanks
7. Scepter 20 Gallon Military-Style Fuel Can: Portable Option
Based on our research, the Scepter 20 gallon can is not a traditional auxiliary tank but a portable solution for those who need occasional extra fuel. It is rugged, stackable, and meets safety standards for diesel storage. However, it requires manual pouring, which can be awkward with a full 20-gallon can (weighing about 140 pounds). It is best used as a backup or for off-grid refueling.
Who should skip it: If you want a plumbed-in auxiliary tank that automatically feeds your engine, this is not for you. Also, if you have physical limitations, the weight of a full can may be prohibitive.
- 20 gallon capacity with NATO-style spout
- Stackable, leak-proof design with vented cap
- Meets military and UN standards for fuel storage
Pros: Highly portable and easy to store when empty; Extremely durable polyethylene resists dents and corrosion
Cons: Manual pouring can be messy and slow; Not a permanent tank; requires manual transfer to main tank
Frequently Asked Questions
Do auxiliary tanks require professional installation?
It depends on the type. Replacement tanks that integrate with the factory fuel system typically require professional installation due to fuel line modifications and safety considerations. Bed-mounted or portable tanks are often DIY-friendly with basic mechanical skills. Always follow the manufacturer’s instructions and local regulations.
Are auxiliary tanks legal for on-road use?
Yes, as long as they meet DOT and EPA requirements for diesel storage. Most tanks we reviewed are compliant, but you should verify that the tank is CARB-approved if you live in California. Also, some states have limits on total fuel capacity, so check local laws.
How do I transfer fuel from an auxiliary tank to my main tank?
Many auxiliary tanks come with a manual pump or a 12V electric pump. Some systems use a gravity feed or a transfer pump that automatically refills the main tank when the level drops. We recommend an electric pump with a filter for convenience and safety.
Will an auxiliary tank void my truck's warranty?
Modifications to the fuel system can potentially void parts of the warranty if they cause damage. However, using a quality tank and professional installation minimizes risk. Check your warranty terms and consider using a dealer-approved or OEM-style replacement tank.
What is the best material for a diesel auxiliary tank?
Aluminum is lightweight, rust-proof, and durable, making it ideal for permanent installations. Steel is heavier and can rust but is more affordable. Polyethylene is light and corrosion-resistant but can warp in heat and may be slightly porous. For most users, aluminum offers the best balance.
Our Verdict
After our research and comparison, the Transfer Flow 50 Gallon Replacement Fuel Tank earns the top spot for its seamless integration, high-quality aluminum construction, and maximum range without sacrificing bed space. The RDS Manufacturing 60 Gallon Transfer Tank is a strong runner-up, offering great value and ease of installation for those who can spare bed space. Choose based on your truck’s fitment and whether you prioritize bed utility or cost.
