Frequently Asked Questions About Peterbilt 387 Fuel Tank Caps

Will these fuel tank caps fit my specific year Peterbilt 387?

Our Peterbilt 387 fuel tank caps are designed to fit models from 1999 through 2010. These caps feature standard threading that matches OEM specifications for all 387 models within this production range. However, if your truck has aftermarket fuel tanks or modified fuel systems, we recommend measuring your current cap's diameter and thread pitch before ordering. Most 387 models use either a 2.5" or 3.5" diameter cap with standard right-hand threads.

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

Locking fuel caps provide theft deterrence and prevent fuel contamination from tampering. They typically come with 2 keys and use a spring-loaded locking mechanism. Non-locking caps offer quicker access for frequent fueling but rely solely on the threading to stay secure. For owner-operators or fleet vehicles parked in unsecured areas, we strongly recommend locking caps. The locking mechanism adds about 1/4" to the overall height, so ensure you have clearance if using side fairings.

Are chrome or aluminum fuel caps better for long-term durability?

Chrome-plated steel caps offer superior durability and resist denting better than aluminum, but they're heavier and can show rust if the chrome chips. Aluminum caps are lighter, won't rust, and maintain their appearance longer in harsh weather conditions. For trucks operating in salt-heavy regions or coastal areas, aluminum is the better choice. Chrome caps typically last 5-7 years with proper care, while quality aluminum caps can last 10+ years.

How do I know if I need a vented or non-vented fuel cap?

Peterbilt 387 models manufactured before 2004 typically require vented caps to prevent vacuum buildup in the fuel tank. Models from 2004 onward usually have separate tank venting systems and use non-vented caps. Using the wrong type can cause fuel pump issues, poor engine performance, or tank damage. Check your owner's manual or look for a separate vent line on your fuel tank. When in doubt, vented caps are the safer option as they won't harm newer systems.

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

Installation is straightforward and takes less than 5 minutes per cap. First, clean the filler neck threads with a wire brush to remove debris. Apply a thin layer of anti-seize compound to prevent thread galling, especially important with aluminum caps on steel tanks. Hand-tighten until the gasket makes contact, then turn an additional 1/4 to 1/2 turn. Over-tightening can damage the gasket and cause leaks. Replace the rubber gasket every 2-3 years or if you notice any fuel odor around the cap area.