Peterbilt 359 Fuel Tank Caps

Frequently Asked Questions About Peterbilt 359 Fuel Tank Caps

Will these fuel tank caps fit my specific year Peterbilt 359?

Most aftermarket fuel tank caps for the Peterbilt 359 are designed to fit all model years from 1967 to 1987. However, some early models (1967-1971) may have slightly different tank openings. We recommend measuring your tank opening diameter before ordering - standard openings are typically 4 inches for diesel tanks. If you're unsure, contact us with your OEM and we can verify compatibility.

What's the difference between vented and non-vented fuel caps?

Vented caps allow air to enter the tank as fuel is consumed, preventing vacuum buildup that can cause fuel flow problems. Non-vented caps create a complete seal. For Peterbilt 359 trucks, you'll need at least one vented cap per tank system. If you have dual tanks, typically the primary tank uses a vented cap while the secondary can use either type. Using all non-vented caps can cause fuel starvation and pump damage.

Are locking fuel caps worth the extra cost for my Peterbilt 359?

Locking fuel caps are highly recommended, especially if you park in unsecured areas or truck stops frequently. Diesel theft is common, and a quality locking cap costs far less than a tank of stolen fuel. Look for caps with sturdy brass tumblers rather than plastic internals. Most locking caps come with 2-3 keys, and you can order matching lock sets if you want all your caps keyed alike.

How do I know if my fuel cap is causing my check engine light?

A faulty fuel cap is one of the most common causes of evaporative emission codes on newer Peterbilt 359 models with emissions equipment. Signs include a strong fuel smell, visible cracks in the cap gasket, or difficulty tightening the cap. The cap should click 3-4 times when properly tightened. If your check engine light appeared shortly after refueling, try replacing the cap first before expensive diagnostics.

What material and finish options last longest on Peterbilt 359 fuel caps?

Aluminum caps with polished or chrome finishes are popular for show trucks but require regular maintenance to prevent oxidation. For durability, powder-coated steel or stainless steel caps hold up best against weather and fuel spills. Avoid plastic caps on commercial trucks as they become brittle from UV exposure and temperature cycles. Always check that replacement caps include a quality rubber or Viton gasket for proper sealing.