Auxiliary Fuel Tanks for Pickup Trucks: A Complete Guide
If you’re a truck owner who regularly tackles long hauls, tows heavy loads, or ventures far off the beaten path, running out of fuel isn’t just an inconvenience—it’s a serious risk. An auxiliary fuel tank for your pickup truck is the ultimate solution, dramatically extending your range and freeing you from the anxiety of constantly searching for the next gas station. This comprehensive guide will walk you through everything you need to know, from the different types of tanks to the critical installation details, helping you make an informed decision that perfectly suits your driving needs. Investing in a high-quality auxiliary fuel system is a game-changer for anyone who depends on their truck for work or adventure.
Why Consider an Auxiliary Fuel Tank?
The primary reason for adding a secondary fuel tank is simple: more miles between fill-ups. But the benefits go far beyond just convenience.
- Unmatched Range and Convenience: Double or even triple your driving range. This is a huge advantage for cross-country road trips, remote job sites, and overlanding expeditions where fuel stops can be few and far between.
- Enhanced Towing Capability: Towing a heavy trailer decimates your fuel economy. An auxiliary tank ensures you can cover significant distances without detouring for fuel, making long-haul towing much less stressful.
- Potential for Fuel Savings: You can take advantage of buying fuel in bulk when prices are low, rather than being forced to fill up at expensive, remote stations.
- Increased Safety and Peace of Mind: Knowing you have a substantial fuel reserve allows you to confidently explore remote areas and handle unexpected detours or emergencies.
Types of Auxiliary Fuel Tanks
Not all auxiliary fuel tanks are created equal. The right choice depends on your truck’s model, your intended use, and your budget. Here are the main configurations you’ll encounter.
In-Bed Fuel Tanks
These are the most versatile and universally compatible tanks. They sit in your truck bed and are available in various shapes and sizes, from rectangular cross-bed boxes to low-profile saddle tanks that fit along the bed walls.
Pros: Easy to install and remove; fits almost any pickup truck; no permanent modification required.
Cons: Takes up valuable cargo space in the bed; can be less secure from theft if not properly mounted.
Replacement Fuel Tanks
This option involves replacing your factory fuel tank with a much larger one. These are often designed to fit within the same frame space but with a significantly higher capacity.
Pros: Maintains all your truck bed space; provides a sleek, OEM-like look and function.
Cons: Typically the most expensive option; installation is complex and often best left to professionals.
Transfer Flow Auxiliary Tanks
Transfer Flow is a leading manufacturer in this industry, and their systems are worth a specific mention. They offer a range of in-bed and replacement tanks that are DOT-compliant and CARB-certified, which is crucial for legal operation in all 50 states. Many of their systems integrate seamlessly with your truck’s existing fuel gauge and onboard computer.
Key Considerations Before You Buy
Choosing an auxiliary fuel tank isn’t just about picking the biggest one. Several critical factors will determine the best system for your vehicle.
Material: Steel vs. Polyethylene
The tank’s construction material impacts its durability, weight, and corrosion resistance.
- Steel Tanks: Extremely durable and robust, ideal for harsh, off-road conditions. The downside is that they are heavier and can be susceptible to rust over time if not properly coated or maintained.
- Polyethylene Tanks: Made from cross-linked polyethylene, these tanks are lightweight and completely impervious to rust. They are a fantastic choice for most users, offering excellent impact resistance and a long service life.
Fuel Tank Capacity and Your Needs
Capacity is measured in gallons. Think carefully about how much extra range you truly need. A 40-gallon auxiliary tank might sound great, but it adds over 250 pounds of weight when full. This can affect your payload and fuel economy. For most users, a tank in the 30 to 60-gallon range offers the best balance of added range and practical weight.
DOT and CARB Compliance
This is non-negotiable. In the United States, auxiliary fuel tanks must be compliant with Department of Transportation (DOT) standards. If you live in or travel to California, the tank must also be certified by the California Air Resources Board (CARB). Using a non-compliant tank can result in hefty fines. Always check the manufacturer’s certification before purchasing.
Installation: DIY or Professional?
The complexity of installing a secondary fuel tank varies widely. A simple, gravity-fed in-bed tank might be a straightforward DIY project for a confident home mechanic. However, systems that integrate with your main fuel tank, involving electric transfer pumps and complex plumbing, are a different story.
Mike Reynolds, a certified master technician with over 20 years of experience, advises, “For any system that taps into your factory fuel lines or requires electrical work connected to the vehicle’s main harness, professional installation is highly recommended. A proper installation is critical for both vehicle performance and, most importantly, safety.”
Improper installation can lead to fuel leaks, vapor lock, or even fire hazards. The peace of mind that comes with a professional, warranty-backed installation is often worth the extra cost.
Comparing Popular Auxiliary Fuel Tank Options
| Feature | In-Bed Tank | Replacement Tank | Transfer Flow System |
|---|---|---|---|
| Best For | Versatility, easy removal | Maximizing bed space, OEM look | Seamless integration, full compliance |
| Installation Complexity | Low to Moderate | High | Moderate to High |
| Average Cost | $500 – $1,500 | $1,200 – $3,000+ | $800 – $2,500 |
| Capacity Range | 20 – 100+ gallons | 30 – 70 gallons | 20 – 100+ gallons |
| Key Advantage | Universal fit | Preserves cargo area | DOT/CARB certified, reliable |
Maintenance and Safety Best Practices
Once installed, your auxiliary fuel tank requires minimal but consistent maintenance.
- Regular Inspections: Periodically check all fuel lines, connections, and the tank itself for any signs of wear, damage, or leaks.
- Use a Fuel Additive: If the fuel will sit for long periods, especially with modern ethanol-blended gasoline, use a fuel stabilizer to prevent degradation and moisture buildup.
- Monitor Your Transfer System: If you have a pump-based system, listen for unusual noises and ensure it transfers fuel at the expected rate.
- Keep it Full: A mostly full tank has less air space, which reduces the potential for condensation and internal corrosion.
According to a report by the National Highway Traffic Safety Administration (NHTSA), properly maintained fuel systems are integral to overall vehicle safety. Ensuring your auxiliary setup is part of your regular vehicle check-up routine is a simple but effective safety measure.
Frequently Asked Questions
Is it legal to install an auxiliary fuel tank on my pickup truck?
Yes, it is legal provided the tank is DOT-compliant. If you reside in California, the tank must also have a CARB Executive Order (EO) number. Always verify the manufacturer’s certifications for your specific state’s regulations.
How does the fuel transfer from the auxiliary tank to the main tank?
There are two primary methods. Gravity-fed systems use a simple hose and the force of gravity, but they require the auxiliary tank to be mounted higher than the main tank. Electric pump systems are more common and versatile, using a 12-volt pump to actively transfer fuel, often with a switch on your dashboard.
Will an auxiliary fuel tank void my truck’s warranty?
Under the Magnuson-Moss Warranty Act, a manufacturer cannot void your vehicle’s warranty simply for adding an aftermarket part. However, if they can prove that the auxiliary tank or its installation directly caused a failure (e.g., in the fuel system), they may deny coverage for that specific repair. Using a certified professional for installation helps protect your warranty.
Can I use my factory fuel gauge for the auxiliary tank?
Some high-end, integrated systems can display the auxiliary fuel level on your truck’s dashboard. Most systems, however, come with their own separate gauge that you will need to mount in the cab.
What is the typical lifespan of an auxiliary fuel tank?
With proper care, a high-quality steel or polyethylene auxiliary fuel tank can last the entire lifetime of your truck. The key factors are the quality of the installation and consistent, basic maintenance.
Sources and Further Reading:
Transfer Flow, Inc.
National Highway Traffic Safety Administration (NHTSA) – Fuel Systems
California Air Resources Board (CARB)
