How to Choose the Right In-Line Fuel Filter Size

By DeatschWerks | Published: 2026-10-22

Category: How-to Guides

Selecting the correct in-line fuel filter size means matching micron rating, connection type, and housing length to your fuel system's flow and pressure needs. This guide breaks down the key factors.

Quick answer

Choose an in-line fuel filter size by first matching the micron rating to your injector type (5 micron for high-pressure EFI, 10 micron for most other systems), then selecting a connection size (hose barb or AN) that fits your fuel line, and finally picking a housing length that fits your mounting space.

Micron rating: the first decision point

The micron rating determines how fine a particle the filter can catch. A 5 micron fuel filter traps smaller particles than a 10 micron filter. For modern high-pressure fuel injection systems with sensitive injectors, a 5 micron filter is typically recommended to protect against clogging. For carbureted setups, throttle-body injection, or many return-style systems, a 10 micron filter provides sufficient protection without excessive flow restriction.

Keep in mind that a finer filter can create more pressure drop, especially at high flow rates. If your system demands over 1000 liters per hour, a 10 micron filter with a larger surface area may be a better balance of protection and flow.

Connection type: hose barb vs. AN fitting

In-line fuel filter kits come with either hose barb connections or AN (AN fitting) connections. Hose barbs (e.g., 5/16 in or 3/8 in) are straightforward to install with standard rubber fuel hose and clamps, making them a common choice for street cars and restoration projects. AN fittings (e.g., -6AN) use a threaded, reusable connection that is preferred for high-pressure, race, or custom builds where you want a leak-proof seal and the ability to disassemble easily.

Your existing fuel line size dictates the connection choice. If you already have -6AN lines, choose an AN filter. If you are using rubber hose, match the barb size to the hose inner diameter.

Housing length and packaging constraints

Housing length (e.g., 70mm, 110mm, 160mm) determines the filter element's surface area and how much space the filter occupies. A longer housing generally offers more filtration area, which can reduce flow restriction and extend service intervals. However, you must ensure the filter fits in your engine bay, under the chassis, or along the frame rail without interfering with other components.

Measure your available mounting space before buying. Universal fitment kits like those from DeatschWerks give you flexibility, but you still need to confirm physical clearance.

Decision rules for selecting your in-line fuel filter size

1. Match micron to injector type: Use a 5 micron fuel filter for high-pressure direct injection or sensitive multi-port injectors. Use a 10 micron fuel filter for carburetors, throttle-body injection, or return-style systems where flow is a higher priority.
2. Pick connection to match your fuel line: If you use rubber fuel hose, select a filter with a hose barb (5/16 in or 3/8 in) that matches your hose inner diameter. If you use AN fittings, choose a filter with the same AN size (e.g., -6AN). Measure your existing line or fitting before ordering.
3. Choose housing length by space and flow needs: Longer housings (160mm) provide more filtration area and less restriction, but need more mounting space. Shorter housings (70mm, 110mm) fit tighter areas but may need more frequent changes. Verify clearance in your vehicle. If space is very tight, a 70mm filter works; if you can fit 160mm, you get longer service life.

Fuel filter options at a glance

5/16 in, 5 micron, 160mm In-line fuel filter kit: DeatschWerks 5/16 in, 5 micron, 160mm In-line fuel filter kit with stainless steel element and hose barb connection. The 5 micron rating suits high-pressure EFI systems, while the 5/16 in barb fits common 5/16 in fuel hose; the 160mm length provides ample filtration area for steady flow.
5/16 in, 5 micron, 160mm In-line fuel filter kit
3/8 in, 10 micron, 160mm In-line fuel filter kit: DeatschWerks 3/8 in, 10 micron, 160mm In-line fuel filter kit with a 1000+ lph flow rating and stainless steel element. The 10 micron rating and high flow capacity make it a solid choice for return-style systems or higher-horsepower builds that need less restriction.
3/8 in, 10 micron, 160mm In-line fuel filter kit
-6AN, 5 micron, 70mm In-line fuel filter kit: DeatschWerks -6AN, 5 micron, 70mm In-line fuel filter kit with stainless steel element and AN connections. The -6AN connection is ideal for race or custom AN-line setups, and the compact 70mm housing fits tight spaces, but the shorter element may require more frequent changes.
3/8 in, 10 micron, 110mm In-line fuel filter kit: DeatschWerks 3/8 in, 10 micron, 110mm In-line fuel filter kit with stainless steel element and hose barb connections. A middle-ground housing length that balances filtration area and space savings, suitable for many street and mild performance builds using 3/8 in hose.

Who should choose which filter

Best for

Builders with high-pressure EFI systems needing fine filtration: choose a 5 micron filter with hose barb or AN connection matching your line.
Street performance or mild builds using 3/8 in hose: a 10 micron, 110mm or 160mm filter balances flow and protection.

Not for

Systems already plumbed with -8AN or larger lines: these filters use -6AN or hose barb connections, so you would need adapters or a different filter.
Extreme high-flow racing applications exceeding 1000 lph: while the 10 micron 160mm filter handles 1000+ lph, a larger dedicated filter may be needed for sustained high flow.