Frequently Asked Questions About Peterbilt 389 Glider Fuel Tank Caps

Will these fuel tank caps fit my specific year Peterbilt 389 glider?

Our Peterbilt 389 glider fuel tank caps are designed to fit all 389 glider models from 2007 to present. These caps use the standard Peterbilt threading pattern and are compatible with both aluminum and steel tanks. However, if your truck has aftermarket tanks or custom modifications, we recommend measuring your existing cap diameter (typically 4 inches for standard caps or 5 inches for large mouth versions) to ensure proper fitment.

What's the difference between locking and non-locking fuel caps, and which should I choose?

Locking fuel caps feature a key mechanism that prevents unauthorized access to your fuel tank, providing security against fuel theft and tampering. Non-locking caps offer quicker access for frequent fueling but lack security features. Most drivers hauling through high-theft areas or parking overnight in unsecured locations prefer locking caps. Both types maintain the same seal quality and pressure ratings, so your choice depends primarily on your security needs and route patterns.

Are these caps vented or non-vented, and why does it matter?

Most of our Peterbilt 389 fuel caps are vented designs, featuring a pressure relief valve that allows air to enter the tank as fuel is consumed, preventing vacuum lock and ensuring smooth fuel flow to your engine. Non-vented caps are typically only used on auxiliary or secondary tanks. Using the wrong type can cause fuel starvation, poor engine performance, or tank damage. Check your original cap or owner's manual to confirm which type your system requires.

What materials and finishes are available, and how do they hold up?

We offer fuel caps in chrome-plated steel, polished aluminum, and powder-coated aluminum finishes. Chrome-plated steel caps provide excellent durability and shine but may show wear in harsh winter conditions with road salt. Polished aluminum caps are lighter and won't rust but require more frequent polishing to maintain their appearance. Powder-coated options offer the best corrosion resistance and come in various colors to match your truck's scheme, though they may show scratches more easily than metal finishes.

Can I install these myself, and what should I watch out for?

Installation is straightforward and requires no special tools - simply unscrew your old cap and thread on the new one. However, always check the O-ring or gasket condition before installation and apply a thin layer of fuel-resistant lubricant to ensure a proper seal. Hand-tighten until the cap seats firmly against the tank opening, but avoid over-tightening which can damage the threads or gasket. If you notice any fuel odor or see staining around the cap after installation, the gasket may need replacement or the cap may not be fully seated.