Frequently Asked Questions About Mack CH/CHN/CHU Truck Fuel Tank Caps
Will these fuel tank caps fit my specific Mack CH, CHN, or CHU model year?
These fuel tank caps are designed to fit Mack CH, CHN, and CHU models from 1988 through 2007. The caps feature a standard 4-inch diameter opening that matches the OEM specifications for these model years. However, if your truck has been modified with aftermarket fuel tanks, we recommend measuring your tank opening before ordering to ensure proper fitment.
Are these caps made of aluminum or plastic, and which material is better for long-term use?
We offer both aluminum and high-grade polymer (plastic) options. Aluminum caps provide superior durability and resist cracking in extreme temperatures, making them ideal for harsh weather conditions and heavy-duty use. Polymer caps are lighter weight and more economical while still providing reliable sealing. For trucks operating in extreme cold or with frequent fuel cap removal, we recommend aluminum for its longevity.
Do these caps come with a locking mechanism, and are the keys universal or unique?
Yes, we carry both locking and non-locking versions. Our locking fuel caps come with two keys that are uniquely coded to your specific cap - they are not universal. This provides better security against fuel theft. The locking mechanism is built into the cap design and adds approximately 1/2 inch to the overall height compared to non-locking versions.
How do I know if I need a vented or non-vented fuel cap for my Mack truck?
Most Mack CH/CHN/CHU trucks from 1988-2007 require vented fuel caps to prevent vacuum buildup in the tank. If your original cap has small holes or slots near the seal area, you need a vented cap. Using a non-vented cap on a system designed for venting can cause fuel pump problems and poor engine performance. When in doubt, check your owner's manual or contact us with your VIN for verification.
What's involved in installing these caps, and will they seal properly without leaking?
Installation is straightforward - simply remove your old cap and thread the new one on by hand until snug. These caps feature heavy-duty rubber O-ring seals that create a tight seal when properly installed. Avoid over-tightening, as this can damage the seal. If you experience any leaking, check that the tank neck threads are clean and undamaged. Replace the O-ring seal every 2-3 years or if you notice any cracking or deterioration.
