Frequently Asked Questions About GMC Brigadier Truck Fuel Tank Caps

Will these fuel tank caps fit my specific year GMC Brigadier, and are they compatible with both saddle tanks and step tanks?

Our GMC Brigadier fuel tank caps are designed to fit models from 1988-1998. They're compatible with both 50-gallon saddle tanks and 100-gallon step tanks. The caps feature a standard 2-inch NPT thread pattern that matches OEM specifications. However, if your truck has aftermarket tanks or modified fuel systems, we recommend measuring your existing cap's thread diameter before ordering to ensure proper fitment.

Are these caps vented or non-vented, and which type do I need for my Brigadier?

We carry both vented and non-vented options. Most GMC Brigadiers require vented caps to prevent vacuum buildup in the tank and ensure proper fuel flow. Vented caps have a small breather valve that allows air exchange while preventing fuel spillage. Non-vented caps are typically used only on trucks with separate tank venting systems. Check your owner's manual or look for a separate vent line on your tank to determine which type you need.

What's the difference between locking and non-locking caps, and are the locks universal?

Locking fuel caps add security against fuel theft and tampering. Our locking caps come with two keys and use a cam-lock mechanism that's proven reliable in commercial applications. The locks are not universal - each cap has a unique key code. Non-locking caps are more convenient for fleet operations where multiple drivers need access. Both types seal equally well and meet DOT requirements for fuel containment.

How do I know if my fuel cap needs replacement, and what problems can a bad cap cause?

Replace your fuel cap if you notice: fuel odor around the tank area, visible cracks in the rubber gasket, difficulty tightening the cap, or if your check engine light comes on (often code P0457 for EVAP leak). A failing cap can cause poor fuel economy, failed emissions tests, and water contamination in your fuel. The rubber gasket typically lasts 3-5 years depending on climate and use conditions.

Are these caps made of plastic or metal, and which material holds up better for commercial use?

We offer both aluminum and high-grade polymer caps. Aluminum caps are more durable and resist UV damage better, making them ideal for trucks exposed to harsh weather. They typically last 7-10 years. Polymer caps are lighter and more economical, lasting 3-5 years on average. Both meet OEM pressure ratings of 3-5 PSI. For heavy commercial use or extreme climates, we recommend aluminum caps for their superior longevity.