OURWILLSM Locking Diesel Fuel Cap Pair 2PCS for 3½" Fill Tubes – Aluminum, 4 Keys & Rubber Seal

OURWILLSM 2PCS Locking Diesel Fuel Cap with 4 Keys is a pair of heavy‑duty aluminum locking caps that secure diesel tanks on older Freightliner, Kenworth, Peterbilt and Western Star trucks.

This locking diesel fuel cap replaces worn or non-locking caps and is built to resist corrosion while preventing unauthorized access to your tank. Each kit includes two caps, four matching keys, a rubber sealing ring, a safety chain and a crossbar so you can install and use immediately. Designed for specific model year ranges and matching part numbers (572.1036, SNV431089, K071-385-1234), it fits diesel fill tubes with a nominal 3 1/2" diameter and 5 1/2 threads per inch—measure before ordering.

Which trucks and part numbers is this cap compatible with?

This cap is made as a replacement for older heavy‑duty truck models: Freightliner before 1984, Kenworth after 1984, Peterbilt before 1980 and Western Star before 1983. It corresponds to common replacement numbers so you can confirm fitment against your existing cap.

• Compatible model ranges: Freightliner <1984, Kenworth >1984, Peterbilt <1980, Western Star <1983
• Replacement numbers: 572.1036, SNV431089, K071-385-1234
• Diesel use only—verify thread count and diameter before purchase

How durable and secure are these locking caps?

Each cap is cast from aluminum alloy for corrosion and oxidation resistance, giving longer service life compared with cheaper plastics. The included lock cylinders are high quality and come with four matching keys to let you secure both caps easily.

• Aluminum alloy body resists rust and wear
• Quality lock cylinders with 4 keys prevent theft or tampering
• Safety chain and crossbar included for secure installation

Do these caps prevent leaks and vapor loss?

The caps include a rubber sealing ring that forms a tight gasket against the fill tube to reduce fuel vapor escape and leakage. Proper sealing helps protect fuel economy and reduces the chance of fumes entering the cab area, provided the cap matches your fill tube dimensions.

• Rubber seal ensures a snug, leak‑resistant fit
• Tight closure reduces vapor emissions when installed correctly
• Helps maintain safer vehicle environment and fuel containment

How easy is installation and what size should I order?

These caps ship 100% new and are ready to install right out of the box—no special tools required beyond basic hand tightening. Confirm fit by measuring your current cap or the fill tube: nominal size is 3 1/2" with 5 1/2 threads per inch. The product includes a protective blue film that should be peeled off before use.

• Quick, bolt‑on replacement—saves a trip to the shop
• Nominal size: 3 1/2" diameter, 5 1/2 TPI—measure to confirm
• Blue protective film applied; remove before installation

Who is this for: Drivers, fleet managers, and truck owners who operate older Freightliner, Kenworth, Peterbilt or Western Star diesel rigs and need a robust, locking replacement cap. It’s ideal for anyone seeking a corrosion‑resistant aluminum cap with reliable sealing and keyed locking to deter fuel theft and secure equipment during storage or long hauls. If you’re unsure about fit, measure your fuel filler tube diameter and thread pitch first or contact our support for assistance.