Does it cover both diesel and DEF caps?

Yes. On F-550, F-600, and Ram 5500, the RV Fuel Vault covers both diesel and DEF caps.

How much is diesel fuel theft costing RV owners?

With diesel at $4-$5/gallon and tank sizes of 50-80 gallons, a single siphoning event can cost $200-$400+.

Does it fit my diesel motorhome?

Ford F-550, F-600, and Ram 5500 Super C chassis. Use our Fitment Finder.

Limited Lifetime Warranty plus a 30-day satisfaction guarantee.

The Part the Factory Forgot

RV Diesel Fuel Cap Cover — Protect Your Diesel Investment

Diesel fuel is expensive. Diesel engine repairs are even more expensive. The RV Fuel Vault secures your diesel motorhome fuel system with a locking cap cover purpose-built for RVs.

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

✖Diesel fuel costs $4-$5+ per gallon — a full tank is worth $200-$400
✖Exposed diesel caps on Super C motorhomes invite fuel theft
✖Contamination of your diesel system can destroy injectors and turbo — $5,000-$15,000+ repairs
✖Generic diesel cap locks are designed for trucks, not motorhome filler necks
✖Diesel motorhomes are bigger targets because thieves know diesel is valuable

Why a Locking Fuel Door Beats a Locking Gas Cap

Purpose-built for diesel motorhome filler neck configurations
Factory-finished look on your Super C or diesel pusher
Tamper-resistant keyed lock stops diesel theft and contamination
Also covers DEF cap on applicable chassis (F-550, F-600, Ram 5500)
Bolt-on in 8-15 minutes — no drilling, no cutting
Fits Ford F-550, F-600, and Ram 5500 diesel Super C chassis

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 RV Models — Which Locking Fuel Door Fits Your Motorhome?

The RV Fuel Vault diesel cover fits Ford F-550, F-600, and Ram 5500 Super C chassis.

Manufacturer	Models / Floorplans
Ford F-550	Thor Magnitude/Omni, Dynamax Force/DX3, Entegra Accolade, Jayco Seneca
Ford F-600	Thor Magnitude/Omni Super C, Entegra Accolade XL
Ram 5500	Dynamax Isata 5, Grand Design Lineage

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

Frequently Asked Questions

Common questions about The RV Fuel Vault

Not Sure If It Fits Your Rig?

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

Find My Fit

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