Under Bed Auxiliary Fuel Tanks For Pickup Trucks: Expanding Your Horizon

Under Bed Auxiliary Fuel Tanks For Pickup Trucks: Expanding Your Horizon pickup.truckstrend.com

For pickup truck owners, the open road often calls, but so too does the need for extended range, especially when venturing off the beaten path, tackling remote job sites, or simply seeking to bypass overpriced fuel stops. This is where under-bed auxiliary fuel tanks emerge as an indispensable solution. Unlike in-bed transfer tanks that occupy valuable cargo space, these cleverly designed reservoirs integrate seamlessly beneath the truck bed, offering a stealthy and efficient way to significantly boost your fuel capacity.

An under-bed auxiliary fuel tank is essentially a secondary fuel storage unit, typically mounted between the frame rails of a pickup truck, often replacing the spare tire or occupying otherwise unused space. It connects to your truck’s primary fuel system, either through a sophisticated transfer pump or a gravity-fed system, allowing you to access additional fuel at the flick of a switch or through a manual valve. Their growing popularity stems from their ability to provide peace of mind, greater autonomy, and practical benefits for a wide range of applications, from long-haul towing and overlanding adventures to commercial use and emergency preparedness.

Under Bed Auxiliary Fuel Tanks For Pickup Trucks: Expanding Your Horizon

Why Consider an Under Bed Auxiliary Fuel Tank?

The decision to install an under-bed auxiliary fuel tank is often driven by a desire for enhanced capability and convenience. Here are the compelling benefits:

• Extended Range: This is the most obvious advantage. Doubling your fuel capacity means fewer stops for fuel, allowing you to cover vast distances without interruption. This is invaluable for cross-country trips, remote expeditions, or simply reducing the frequency of fill-ups.
• Convenience and Time Savings: Imagine bypassing crowded gas stations or avoiding detours to find fuel. With an auxiliary tank, you can refuel at your leisure, saving precious time on long journeys or busy workdays.
• Fuel Cost Savings: For those who travel frequently, the ability to fill up when prices are low, or to carry fuel from regions with cheaper rates, can lead to significant savings over time. It also mitigates the risk of being forced to buy expensive fuel in isolated areas.
• Peace of Mind: "Range anxiety" is a real concern, especially when towing heavy loads, navigating unfamiliar terrain, or operating in areas with limited fuel infrastructure. An auxiliary tank eliminates this worry, ensuring you have ample fuel to reach your destination or return safely.
• Off-Grid and Commercial Capability: For overlanders, campers, farmers, and construction crews, an under-bed tank is a game-changer. It provides the necessary fuel to power generators, run equipment, or simply sustain your vehicle for extended periods away from civilization or refueling points.



• Preserved Cargo Space: Unlike bulky in-bed tanks, under-bed units keep your truck bed completely clear for tools, equipment, cargo, or recreational gear, maximizing the utility of your pickup.

Types of Under Bed Auxiliary Fuel Tanks

Under-bed auxiliary tanks come in various configurations to suit different needs and truck models. Understanding these variations is crucial for making an informed choice:

• Material:
  • Aluminum: Lightweight, corrosion-resistant, and durable. Often the preferred choice for its strength-to-weight ratio and resistance to rust. Generally more expensive.
  • Steel: Very strong and durable, often less expensive than aluminum. However, it’s heavier and susceptible to rust if not properly coated or maintained.
  • Polyethylene (Plastic): Lightweight, impact-resistant, and non-corrosive. More affordable but may have lower capacities or specific application limitations due to material strength.

  

• Capacity: Tanks range widely in size, from 20-gallon compact units to over 100-gallon monsters. Common capacities for under-bed tanks often fall in the 30-70 gallon range, designed to fit within specific frame constraints.
• Transfer Method:
  • Gravity Feed: Simple and reliable, fuel flows from the auxiliary tank to the main tank via gravity. Requires the auxiliary tank to be mounted higher than the main tank’s fill neck. Often includes a shut-off valve.
  • Pump-Based (Electric): Utilizes an electric pump to transfer fuel on demand, typically activated by a switch in the cab. This allows for more flexible tank placement and ensures fuel transfer even on inclines. Some systems are fully automatic, maintaining a certain fuel level in the main tank.
  • Manual Pump: Less common for direct vehicle integration, but some standalone auxiliary tanks may use a hand pump for transfer.
• Integration and Design:
  • Spare Tire Delete: Many under-bed tanks are specifically designed to fit into the space vacated by the spare tire, typically beneath the rear of the truck. This is a popular option as it utilizes otherwise empty space.
  • Frame Rail Mounted: Other designs are elongated or shaped to fit within the frame rails, often requiring careful consideration of exhaust routing, driveshafts, and suspension components.
  • Direct Plumbed vs. Separate Fill: Some systems directly integrate into the truck’s fuel filler neck, using a single fill point for both tanks. Others have a separate fill neck for the auxiliary tank.

Key Considerations Before Installation

Before investing in an under-bed auxiliary fuel tank, a thorough evaluation of several factors is essential to ensure compatibility, safety, and legal compliance.

• Vehicle Compatibility: This is paramount. Not all tanks fit all trucks. Research your specific make, model, year, and bed length. Consider frame clearance, exhaust system routing, driveshaft interference, and suspension components. Some tanks are truck-specific.
• Fuel Type: Auxiliary tanks are designed for either gasoline or diesel. Never mix fuel types. Diesel tanks are generally simpler as diesel is less volatile. Gasoline tanks require more stringent safety measures, including specialized venting and anti-siphon provisions, due to flammability.
• Capacity Needs: How much extra fuel do you genuinely need? Over-specifying can lead to unnecessary weight and cost. Consider your typical travel distances, intended use, and existing fuel economy.
• Legal Regulations: Fuel transfer tanks are subject to state and federal regulations, particularly those concerning hazardous materials transport. DOT (Department of Transportation) compliance is crucial, especially for commercial use. Laws vary regarding maximum capacity, venting requirements, and whether fuel can be transferred while driving. Research local and state laws diligently.
• Weight Distribution and Payload: Fuel is heavy (diesel ~7 lbs/gallon, gasoline ~6 lbs/gallon). A 50-gallon tank adds 300-350 lbs of fuel, plus the weight of the tank itself. This weight must be accounted for in your truck’s payload capacity. It can affect handling, braking, and require suspension upgrades (e.g., airbags, heavier leaf springs) to maintain ride height and stability, especially when towing.
• Installation Complexity: While some mechanically inclined individuals might attempt a DIY installation, it involves working with fuel, electrical systems, and potentially modifying exhaust or frame components. Professional installation by a qualified shop is highly recommended to ensure safety, proper sealing, correct wiring, and compliance with all regulations.
• Cost: Budget for the tank itself, the transfer pump/kit, installation hardware, and potentially professional installation labor. Don’t forget potential ancillary costs like suspension upgrades.
• Warranty: Check if installing an aftermarket fuel tank might affect your truck’s factory warranty, particularly regarding the fuel system.

Installation Process (General Guide)

While professional installation is recommended, understanding the general steps can help you appreciate the complexity:

1. Planning & Safety: Gather all necessary tools. Disconnect the truck’s battery. Ensure a well-ventilated work area. Have a fire extinguisher readily available.
2. Mounting the Tank: The tank must be securely mounted to the truck’s frame using robust brackets and hardware. Ensure adequate clearance from moving parts, hot exhaust components, and the ground. This often involves removing the spare tire if using that space.
3. Fuel Lines & Electrical: Route fuel lines carefully, away from sharp edges and heat sources. Use appropriate fuel-rated hoses and fittings. If using an electric pump, wire it correctly to a switched power source, often with a fuse and relay.
4. Ventilation: Proper venting is critical to prevent pressure buildup or vacuum in the tank, especially for gasoline. Ensure the vent line is routed safely and includes a rollover valve.
5. Filler Neck & Gauge: Install the auxiliary tank’s filler neck in an accessible yet discreet location (e.g., inside the fender well or next to the factory filler). Connect any fuel level senders to a dash-mounted gauge.
6. Connection to Main Tank: This is the most critical step. Depending on the system, it involves either tapping into the main fuel filler neck, a dedicated return line, or a direct connection to the main tank’s fuel pump module (less common for DIY).
7. Testing: After installation, perform thorough leak checks with a small amount of fuel. Test the transfer system functionality. Monitor for any dashboard warning lights.

Maintenance and Usage Tips

To ensure longevity and safe operation of your auxiliary fuel tank:

• Regular Inspections: Periodically check all fuel lines, fittings, and the tank itself for leaks, corrosion, or damage. Ensure mounting hardware remains tight.
• Keep Fuel Fresh: Especially with gasoline, avoid letting fuel sit in the auxiliary tank for extended periods (more than 6 months). Stale fuel can degrade and cause issues. Consider using a fuel stabilizer if storing fuel for long durations.
• Proper Fueling Procedures: Always fill the auxiliary tank slowly to prevent spills and allow for proper venting. Do not overfill.
• Understand Your Transfer System: Know how your specific system operates – whether it’s manual, on-demand electric, or automatic.
• Winter Considerations (Diesel): If carrying diesel in cold climates, ensure the fuel is treated with an anti-gel additive, especially if it’s sitting in the auxiliary tank for a while.
• Filter Maintenance: Some systems include an in-line fuel filter. Replace it according to the manufacturer’s recommendations.

Potential Challenges and Solutions

While beneficial, auxiliary fuel tanks can present certain challenges:

• Weight Impact:
  • Challenge: Added weight reduces payload capacity, can sag suspension, and affect handling/braking.
  • Solution: Install upgraded suspension components (e.g., heavier leaf springs, airbags, aftermarket shocks) to compensate for the added weight and maintain ride quality.
• Legal Hurdles:
  • Challenge: Varying state and federal regulations regarding fuel transfer and hazardous materials.
  • Solution: Thoroughly research and understand all applicable laws before purchase and installation. Ensure your chosen tank and system are DOT compliant.
• Installation Difficulty:
  • Challenge: Complex installation involving fuel, electrical, and structural components.
  • Solution: Opt for professional installation by a reputable shop specializing in truck accessories or fuel systems.
• Cost:
  • Challenge: Initial investment can be significant.
  • Solution: View it as a long-term investment that offers convenience, potential fuel savings, and expanded capabilities that justify the upfront cost.
• Fuel Contamination:
  • Challenge: Risk of introducing contaminants to the main fuel system if the auxiliary tank or fuel is dirty.
  • Solution: Always use clean, quality fuel. Ensure your auxiliary tank has a proper filter and keep its filler area clean.

Under Bed Auxiliary Fuel Tanks: Estimated Price Guide

Please note that these are estimated price ranges and can vary significantly based on brand, material, capacity, features (e.g., type of pump, integration kit), and installation complexity.

Category	Material	Capacity (Gallons)	Estimated Tank Only Price Range (USD)	Estimated Tank + Basic Install Kit Price Range (USD)	Professional Installation Cost (USD)	Total Estimated Cost Range (USD)
Standard Under Bed Tank	Polyethylene	20-40	$400 – $700	$600 – $1,000	$400 – $800	$1,000 – $1,800
Premium Under Bed Tank	Aluminum	30-50	$800 – $1,500	$1,200 – $2,000	$600 – $1,000	$1,800 – $3,000
Large Capacity/Custom Fit	Aluminum	50-70+	$1,500 – $2,500+	$2,000 – $3,500+	$800 – $1,500+	$2,800 – $5,000+
Advanced Systems	Aluminum	30-70	(Included in Kit)	$2,500 – $4,500+ (Includes Auto Pump, Gauge)	$1,000 – $2,000+	$3,500 – $6,500+

• Note on Installation: Professional installation costs vary based on shop labor rates, complexity of the specific truck/tank combination, and any necessary modifications (e.g., exhaust rerouting, suspension upgrades). Always get multiple quotes.
• Additional Costs: May include fuel gauges, specialized filters, or suspension upgrades (airbags: $500-$1500, heavy-duty leaf springs: $300-$800).

Frequently Asked Questions (FAQ)

Q: Are under-bed auxiliary fuel tanks legal?
A: Generally, yes, but legality depends heavily on federal, state, and local regulations. Tanks must be DOT compliant, properly vented, and securely installed. Some states may have specific rules on maximum capacity or whether fuel can be transferred while driving. Always research the laws in your region.

Q: Can I install an under-bed auxiliary fuel tank myself?
A: While possible for experienced DIYers, it’s highly recommended to have a professional install an under-bed auxiliary fuel tank. It involves working with flammable fuel, electrical systems, and critical vehicle components, requiring specialized knowledge and tools to ensure safety and compliance.

Q: Does installing an auxiliary fuel tank void my truck’s warranty?
A: It might. Modifying the fuel system or adding significant weight can potentially void certain aspects of your vehicle’s factory warranty. It’s best to check with your dealership or the truck manufacturer beforehand.

Q: What fuel types can an auxiliary tank hold?
A: Auxiliary tanks are designed specifically for either gasoline or diesel. Never put gasoline in a diesel tank or vice-versa. The materials, venting, and safety features differ significantly.

Q: How do I know what size auxiliary tank to get?
A: Consider your typical driving range, how much extra range you desire, and your truck’s available under-bed space and payload capacity. Measure the space carefully and consult your truck’s specifications. Don’t forget to account for the weight of the fuel itself.

Q: Will an under-bed tank interfere with towing?
A: In most cases, under-bed tanks are designed to avoid interference with hitches and towing. However, the added weight of the tank and fuel will reduce your available payload capacity, which is crucial for safe towing. You may need suspension upgrades to compensate.

Q: How do I transfer fuel from the auxiliary tank to the main tank?
A: Most systems use either an electric pump activated by a switch in the cab or a gravity-feed system with a manual valve. Electric pump systems are more common for under-bed tanks as they don’t rely on elevation differences.

Conclusion

Under-bed auxiliary fuel tanks represent a smart, space-saving solution for pickup truck owners seeking to expand their horizons. They offer unparalleled convenience, extended range, and the peace of mind that comes with knowing you have ample fuel for any journey or task. While the initial investment and the intricacies of installation and legal compliance require careful consideration, the long-term benefits in terms of autonomy, efficiency, and capability are undeniable. By understanding the types, considerations, and proper maintenance, you can confidently equip your truck for whatever adventures or demands lie ahead, truly unleashing its full potential.