Whether you’re new to FASS Diesel Fuel Systems or a long-time diesel enthusiast looking to upgrade, you probably have questions about how FASS works, what makes it different, and how to choose the right system.
In this guide, we’ll answer some of the most commonly searched and asked questions about FASS to help you make informed decisions.
What Does a FASS Diesel Fuel System Do?
A FASS Diesel Fuel System is designed to separate air and vapor, remove over 99% of water, and debris down to 2 Microns—resulting in clean, pressurized fuel delivered to your engine. This protects critical components like injectors and injection pumps while improving throttle response, fuel economy, and reliability.
Originally engineered for commercial trucks, FASS Diesel Fuel Systems have become the #1 fuel filtration upgrade for Class 8 and pickup trucks alike—as well as diesel-powered equipment such as tractors, generators, and more.
What Makes FASS Different from Other Fuel Systems?
FASS systems combine three major functions in one unit:
- Air & Vapor Separation – Removes entrained air that can cause pressure drops, cavitation, hard starts, and injector wear.
- Simply installing a FASS Diesel Fuel System can TRIPLE the life of an injection system.
- Advanced Filtration – Filters down to 2 microns absolute while removing over 99% of the water from your fuel, which is far more effective than stock filters.
- The FASS Extreme Water Separator also serves as a fail-safe against extreme water contamination. Should you ever fill up with a tank of fuel that's full of water, a FASS Diesel Fuel System would prevent the contaminated fuel from reaching your engine.
- Consistent Lift Pump Pressure – Reduces strain on the injection system and ensures stable fuel delivery even under load.
FASS also designs and manufactures its systems in the USA, ensuring tight quality control and innovation that’s trusted across the diesel industry.
Do I Still Need to Use My Factory Fuel Filter?
In many applications, no—FASS filtration will render your factory fuel filter obsolete. Your FASS system will handle the filtration and air separation before the fuel reaches the OEM filter, which means it can be removed or "deleted" in many cases.
For some applications, a separate
Fuel Filter Delete Kit can be purchased to remove the factory fuel filter and/or housing.
How Often Should I Change My FASS Filters?
FASS filters should typically be changed every 20,000 to 30,000 miles, depending on driving conditions and fuel quality. If you operate in dirty or variable fuel environments, consider shorter intervals. If you drive less than 20,000 to 30,000 miles per year, we recommend changing them annually.
Regular filter changes ensure your system continues to deliver clean, air-free fuel—and help prevent power loss, hard starts, or injector wear.
Does Installing a FASS System Void My Warranty?
No. Simply installing a FASS Diesel Fuel System does not void your factory warranty. The Magnuson-Moss Warranty Act prevents manufacturers from voiding your warranty just because you’ve added aftermarket parts—unless they can prove that the part directly caused a failure.
Some dealerships and performance shops actually recommend FASS systems they exceed OEM filtration requirements and improve the life of expensive injection system components.
How Do I Choose the Right Size FASS System?
Choosing the right system depends on:
- Engine & Model Year (Cummins, Duramax, Powerstroke, CAT, Paccar, Detroit, etc)
- Horsepower / Performance Level
- Intended Use (towing, daily driving, performance, competition)
For example, stock or lightly modified trucks may only need a
Drop-In Fuel Series System, while heavily modified or high-horsepower builds often use 220+ GPH systems. We offer Drop-In, Titanium Signature Series, and Industrial Series Fuel Systems to suit every need.
How Hard Is It to Install a FASS System?
Installation difficulty varies by model:
- Drop-In Series: Usually installs in 1–3 hours using factory locations and OEM fuel lines. No cutting or drilling required.
- No-Drop Systems (with sump): Typically more involved but still manageable for experienced DIYers or performance shops. Requires drilling a single hole for the sump.
- Full Titanium Signature Series: Ideal for performance builds or as a long-term upgrade. Professional installation is recommended for best results.
We provide detailed installation instructions with every kit, and our Missouri-based service team is available for step-by-step guidance.
What Kind of Maintenance Does a FASS System Require?
Aside from routine filter changes, maintenance is minimal. When installing, check fittings and lines for leaks, and inspect the wiring and mounting hardware to ensure everything remains secure.
FASS Fuel Systems are designed to outlast the vehicle or equipment they're installed on—running for hundreds of thousands of miles with minimal attention.
Can a FASS System Improve Fuel Economy?
Yes, in many cases. By eliminating air and vapor and improving filtration, a diesel engine will operate as efficiently as possible. Customers often report modest MPG gains, especially when towing or under load—but we cannot guarantee a measurable MPG gain.
This is due to variations in driving habits, MPG tracking methods, and fuel quality—among other factors.
Where Can I Buy Replacement Filters and Parts?
Genuine FASS filters, accessories, and replacement parts are available through the official FASS website, authorized dealers, and many diesel performance shops across the country. Always use genuine parts to maintain system performance and warranty.
Final Thoughts
A FASS Diesel Fuel System is more than just a lift pump—it’s a complete fuel conditioning and protection solution designed for modern diesel engines.
Whether you drive a daily Cummins-powered pickup, a tuned Duramax, or a Powerstroke towing rig, FASS delivers cleaner fuel, consistent pressure, and longer injection system life.
By understanding how the system works and following basic maintenance, you’ll get the most out of your investment and keep your diesel running strong for years to come! If you have questions about a FASS Diesel Fuel System for your truck or diesel-powered equipment, contact us today!
- Email: techsupport@Fassride.com
- Phone:
1-866-769-3747
- Support Hours: M – F: 7am to 7pm CST
