Why do old Ford trucks have two gas tanks?
They were built with two tanks to extend range and improve reliability for rural and work use.
Historical purpose: extending range and reliability
In the mid-20th century, fuel infrastructure in many parts of the country was uneven. Gas stations could be far apart, especially in rural areas or on long-haul routes. Ford offered dual gas tanks on a number of trucks as a practical solution for farmers, construction crews, and long-distance drivers. The extra tank meant fewer fuel stops, a built-in reserve, and a steadier supply to the engine when the primary tank ran low. While not all Ford trucks had dual tanks, the configuration became a recognizable option on several models from the 1950s through the 1970s and beyond.
How the dual-tank system works
Here is how the two-tank arrangement typically operated in classic Ford pickups.
- Tank locations and capacities: there were usually two tanks mounted along the frame — often a smaller front tank near the cab and a larger rear tank toward the back of the truck.
- Fuel routing: both tanks could feed the engine through the vehicle’s fuel system, with a selector valve or dash switch to choose which tank supplied fuel.
- Fuel selector: a lever or switch on the dash (or sometimes a floor-mounted control) let the driver choose the primary tank; many setups allowed switching to the second tank as needed.
- Gauge and indicators: some configurations used a single combined fuel gauge, while others offered two gauges or an indicator system showing levels for each tank.
- Maintenance considerations: the dual-tank arrangement added complexity—more hoses, vent lines, and valve mechanisms—so checks for leaks, corrosion, and proper operation of the selector valve were more important than on single-tank rigs.
In practice, drivers would monitor fuel and switch tanks as needed, using the primary tank for normal operation and the secondary tank as a reserve or for extended trips. The system offered tangible benefits for those who worked far from fueling infrastructure and needed dependable range.
Variations by model and era
Different Ford trucks implemented the two-tank setup in distinct ways, and the arrangement evolved over time. The feature appeared on various F-Series pickups and related lines, especially in configurations intended for heavy-duty use, long-haul work, or fleets. While the front and rear tank arrangement was common, exact locations, capacities, and the presence of dual gauges or automatic switching varied by year and option package. As the era progressed and gasoline availability improved, two-tank setups became less common in standard consumer models, though they persisted in some diesel-oriented or specialty configurations and in certain fleets.
- Two-tank configurations were commonly offered as an option or standard on some Ford F-Series trucks from the 1950s through the 1970s, particularly for heavy-duty or fleet-oriented models.
- Typically, the rear tank was larger and served as the main long-range fuel source, while the front tank provided a secondary supply or reserve.
- Model variations meant that some trucks displayed two separate fuel gauges, whereas others used a single gauge that reflected overall fuel in both tanks combined.
- With changes in fuel infrastructure and technology, these multiple-tank systems became less common after the 1980s, though dual-tank setups continue to appear in some modern diesel applications and specialized vehicles.
The dual-tank approach reflected a practical response to mid-century realities: longer distances between towns, fewer fueling options, and a demand for reliability in work environments. The design remains a notable part of Ford’s historical truck lineup.
Buying and maintaining a vintage Ford with two tanks
If you own or are shopping for a vintage Ford truck with two tanks, consider these points to ensure the system is sound and usable today.
- Inspect both tanks for rust, leaks, and denting, especially around seams and filler necks.
- Check the selector valve and associated lines for smooth operation and signs of wear or corrosion.
- Verify fuel gauges or indicators for accuracy; erratic readings can mask actual fuel levels.
- Look for intact vent hoses and proper ventilation between tanks to prevent vapor buildup.
- Plan for parts availability: some components (valves, hoses, fittings) may be scarce or require specialty suppliers or salvage parts.
With proper inspection and maintenance, a two-tank Ford can continue to serve as a capable, era-appropriate vehicle for enthusiasts and collectors who value historical authenticity.
Summary
Old Ford trucks used two gas tanks to extend driving range, provide a reserve supply, and support work in areas with sparse fueling options. The arrangement typically featured a smaller front tank and a larger rear tank, fed by a selector valve or dash switch, with gauges that varied by model. While less common in modern production, dual-tank configurations remain a recognizable hallmark of mid-century Ford trucks and continue to attract restorers who value period-correct engineering.
In brief, the two-tank setup was a pragmatic response to the era’s travel realities—an engineering choice that helped keep trucks moving where fuel stations were few and far between—and it left a lasting imprint on Ford’s truck lineage.
What is the purpose of the auxiliary fuel tank?
AUXILIARY FUEL TANKS are defined by the Vehicle Equipement Safety Commission as an additional fuel tank and any other componets attached directly thereto designed to supplement the vehicle's fuel carrying capability beyond that provided by the vehicle manfacturer.
Do trucks have two fuel tanks?
This setup is often found in heavy-duty work trucks, long-haul rigs, and certain off-road builds. Having two tanks provides clear advantages for those who need reliable fuel capacity for both daily operations and long-distance travel.
How do dual fuel tanks work?
A dual fuel tank system works by allowing a vehicle to draw fuel from two separate tanks, which can be connected by a crossover line, a transfer pump, or an electronic selector valve. Most modern systems use an electronic system to switch between tanks automatically, drawing fuel from one or both tanks simultaneously, and returning unused fuel to one of the tanks. Older or simpler systems may have a manual crossover or a single pump drawing from both tanks.
This video explains how a dual fuel system works for vehicles: 56sPro Diesel RepairYouTube · May 21, 2022
How it works
- Crossover line: Some systems connect the two tanks with a line at the bottom. Fuel is drawn from one tank, and unused fuel is returned to the other, which keeps the fuel levels equal.
- Electronic selector valve: A switch on the dashboard allows the driver to manually select which tank to draw fuel from, or to switch to a reserve tank.
- Transfer pump: Some systems use an electric pump to transfer fuel from one tank to the other to keep the tanks balanced.
- Combined system: Newer trucks often use a combination of these methods. For example, a system might have two tanks connected to a valve block under the cab, which automatically switches between tanks to keep the fuel levels balanced.
- Fuel gauge: The fuel gauge is typically connected to a sender in one of the tanks, but it can be designed to work with either tank, or to switch between the tanks as fuel levels change.
Types of dual fuel systems
- Automated switching: The system switches tanks automatically, based on temperature, cost, and efficiency.
- Manual switching: The driver manually selects the tank to use.
- Combined systems: A combination of automated and manual switching is used.
Key components
- Crossover pipe: A pipe that connects the two tanks, allowing fuel to flow between them.
- Electronic selector valve: A valve that allows the driver to manually select which tank to draw fuel from.
- Transfer pump: An electric pump that moves fuel from one tank to the other.
- Fuel gauge: A gauge that shows the fuel level in the tanks, which may be a single gauge that works with both tanks.
What is the purpose of a double wall fuel tank?
A double-wall tank has an interstitial space between the two walls that fulfills the function of secondary containment in the event of leakage. No external containment safety feature is required in the storage site.
