Freightliner FLC120 Fuel Tanks

Frequently Asked Questions About Freightliner FLC120 Fuel Tanks

What size fuel tanks are available for the Freightliner FLC120, and how do I know which one fits my truck?

Freightliner FLC120 fuel tanks typically come in 50, 75, 100, and 150-gallon capacities. To determine the right fit, check your truck's frame rail measurements and existing tank mounting brackets. Most FLC120 models from 1990-2003 use standard 25-inch or 26-inch diameter tanks. Measure from the bottom of your frame rail to the ground to ensure proper clearance - you'll need at least 16 inches for most tank sizes. Your OEM can help confirm specific mounting configurations if you're unsure.

Are these fuel tanks made of aluminum or steel, and which material is better for my application?

Both aluminum and steel tanks are available for the FLC120. Aluminum tanks are lighter (reducing overall vehicle weight by 50-100 pounds), resist corrosion better, and are ideal for drivers concerned about fuel economy. Steel tanks are typically 20-30% less expensive, more durable against impact damage, and easier to repair if dented. For trucks operating in northern climates with heavy road salt exposure, aluminum is recommended. For heavy-haul or construction applications where impact resistance matters more, steel is often the better choice.

Will I need to replace my fuel tank straps and mounting hardware when installing a new tank?

In most cases, yes. Original tank straps often show signs of corrosion or metal fatigue after years of use, and reusing old straps with a new tank can lead to premature failure. New mounting hardware is recommended for safety and proper fit. Most replacement tanks require 2-inch wide straps for tanks up to 100 gallons, and 2.5-inch straps for 150-gallon tanks. Check that your new tank includes mounting tabs in the same locations as your original - some aftermarket options may require drilling new mounting holes in the frame rails.

Do these replacement tanks come with fuel sending units, or do I need to transfer my old one?

Most replacement fuel tanks for the FLC120 do not include sending units - these are typically sold separately or transferred from your old tank. The sending unit hole is usually pre-cut to accept standard 5-bolt SAE pattern units used on 1990-2003 FLC120 models. When transferring your old sending unit, replace the gasket and check the float arm for damage. New sending units run $75-150 and may be worth purchasing if your fuel gauge has been reading inaccurately.

What's involved in the installation process, and can I do it myself?

Installation typically takes 2-4 hours with basic tools and mechanical experience. You'll need to drain the old tank completely, disconnect fuel lines and electrical connections, and support the tank while removing the straps. Key challenges include handling the weight (empty tanks weigh 50-85 pounds), ensuring proper alignment with existing fuel lines, and achieving the correct strap tension. Many customers report difficulty reaching upper mounting bolts on trucks with dual tanks. Having a helper and a transmission jack or tank cradle makes the job much safer and easier. Always replace fuel line connections and check for leaks before filling the new tank.