Does The RV Fuel Vault cover both diesel and DEF on the F-550?

Yes. Designed to cover and secure both the diesel fuel cap and the DEF cap.

Is DEF contamination really that big a deal?

Yes. Wrong fluid in your DEF tank can destroy your SCR system. Repairs cost $5,000-$10,000+.

Does it fit my specific Super C brand?

Fits Thor Magnitude/Omni, Dynamax Force/DX3, Entegra Accolade, Jayco Seneca, and Renegade. Use our Fitment Finder.

How long does installation take?

8-15 minutes with basic hand tools. No drilling, no cutting.

Limited Lifetime Warranty plus a 30-day satisfaction guarantee.

Is a locking fuel door better than a locking gas cap for an F-550 Super C?

Yes. A locking fuel door covers and shields the entire diesel and DEF filler area, while a locking gas cap only protects the cap threads and often will not fit the commercial F-550 filler neck. The RV Fuel Vault adds a keyed, armored door over the whole assembly, so it stops siphoning, contamination, and tampering a cap alone cannot.

How much does the F-550 locking fuel door cost and where can I buy it?

Pricing starts at $139.95 (Founders Edition) for a single door, $279.95 for a set of two, and $419.95 for the 3-Pack that includes a DEF cover. You buy it directly at thervfuelvault.com with free U.S. shipping and a Limited Lifetime Warranty.

The Part the Factory Forgot

Ford F-550 Locking Fuel Door — The Part the Factory Forgot

The only locking fuel-door enclosure purpose-built for Super C diesel motorhomes on the Ford F-550 chassis. Covers both diesel and DEF caps.

Order Now — From $139.95

Patent Pending Made in USA Free Shipping Ships July 2026

The RV Fuel Vault — Locking Fuel-Door Enclosure — locking fuel door for motorhomes

Why a Locking Gas Cap Is Not Enough

✖Every F-550 Super C leaves the factory with exposed diesel and DEF caps — no fuel door
✖Super C diesel motorhomes carry 50-80 gallons of diesel worth $250-$400 — a theft magnet
✖DEF contamination from tampering can destroy your emissions system — a $5,000-$10,000 repair
✖Generic truck fuel doors do not fit the F-550 Super C motorhome body geometry
✖Your $300K-$500K Super C deserves better than exposed plastic caps

Why a Locking Fuel Door Beats a Locking Gas Cap

Factory-finished look — eliminates exposed diesel and DEF caps
Precision-engineered for the Ford F-550 Super C filler neck configuration
Tamper-resistant keyed lock secures both diesel fuel and DEF fluid
High-strength fiber-filled polymer — built for the rigors of Super C ownership
Bolt-on in 8-15 minutes — no drilling, no cutting
Fits Thor Magnitude/Omni, Dynamax Force/DX3, Entegra Accolade, Jayco Seneca, Renegade

Before & After: Your RV's Exposed Fuel Cap vs. a Locking Fuel Door

✖ Exposed cap — no security

✓ RV Fuel Vault installed

Why You Need a Locking Fuel Door

Lead with finish. End with security.

Factory-Finished Look

Eliminates the exposed plastic cap. Your rig finally looks production complete.

Fuel Theft Prevention

Keyed lock stops siphoning at campgrounds, rest stops, and storage facilities.

Contamination Defense

Prevents sugar, water, or foreign substances from being added to your fuel tank.

Vandalism Protection

Tamper-resistant design deters opportunistic damage to your fuel system.

How It Installs — 8–15 Minutes, No Drilling, No Cutting

8–15 Minutes

Average install time

Basic Hand Tools

No special equipment needed

100% Reversible

No drilling, no cutting, no mods

Compatible Ford F-550 Motorhomes

The Ford F-550 with 6.7L Power Stroke diesel is the backbone of the Super C segment. Both diesel and DEF filler necks are completely exposed from the factory.

Manufacturer	Models / Floorplans
Thor Motor Coach	Magnitude, Omni
Dynamax	Force HD, DX3
Entegra Coach	Accolade
Jayco	Seneca
Renegade	Villagio, Vienna, Explorer

Don't see your model? Use the Fitment Finder — we likely fit your rig.

Frequently Asked Questions

Common questions about The RV Fuel Vault on Ford F-550 motorhomes

Not Sure If It Fits Your Rig?

Our Fitment Finder checks your exact year, make, model, and floorplan in seconds.

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Order Today — Starting at $139.95

Single Door, Set of 2, or 3-Pack · Free Shipping · Limited Lifetime Warranty · 30-Day Guarantee

Order My RV Fuel Vault

Proudly Made in the USA · Patent Pending · Est. delivery by July 31, 2026