Screw-In Filler Neck

Description:
A screw-in filler neck has internal threads, so the fuel cap literally screws in and out to seal the tank.

Typical Features:

• The cap rotates several times to tighten and seal.

• You can feel the threading action as you twist it.

• Common on European and older vehicles (some Mercedes, BMW, Land Rover, etc.).

• Provides a very tight seal — ideal for pressurized or vented systems.

Fuel Angel Fitment:
If your cap screws in like a jar lid, you’ll need the screw-in version of the Fuel Angel.

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Bayonet Filler Neck

Description:
A bayonet filler neck uses lugs or slots instead of threads.
You push in and twist about a quarter turn, and the cap locks in place with a satisfying click.

Typical Features:

• Quick twist-lock design (¼ turn to open or close).

• No visible threads inside the filler neck.

• Common on modern vehicles and vans, including most Mercedes-Benz Sprinters, Ford Transits, and US market cars.

• Designed for fast filling and easy access.

Fuel Angel Fitment:
If your fuel cap just pushes in, turns slightly, and clicks, you need the bayonet version of the Fuel Angel.

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Quick Way to Check

1. Remove your fuel cap.

2. Look inside the filler neck:

   • Threads = Screw-in type

   • Two or three locking slots = Bayonet type

3. If unsure, snap a photo — the pattern of the opening usually makes it clear which version fits.

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✅ In Short:

How It Works

Screw-In-Cap twists multiple times into threads on older or european cars.

Bayonet push-in and quarter-turn to click = Modern vans & cars (e.g., Sprinter)Bayonet

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Images below of some of the different types of screw in filler caps

 

If you cannot see your cap, send us a few photos of your own cap using the form at the bottom of the page and we will match it up for you.