GM GENUINE PARTS Fuel Tank Filler Cap GT329 (23368720) — Threaded with Rubber Gasket & Optional Check Valve

The GM Genuine Parts GT329 (23368720) fuel tank filler cap is an OEM threaded cap with a rubber gasket and optional check valve that seals your vehicle’s fuel filler neck to keep fuel in and contaminants out.

This GM-recommended original equipment replacement is built to match the fit, function, and durability of the factory fuel cap on compatible GM vehicles. Designed to deliver a secure, liquid-tight seal, the cap helps maintain proper tank pressure management while reducing fuel loss and preventing water and dirt from entering the tank. Manufactured to GM standards, it replaces worn or missing caps without modifying the vehicle.

How does this cap protect my fuel system?

The threaded design and integrated rubber gasket form a tight barrier at the fuel filler neck, blocking debris and moisture and helping to prevent fuel seepage. Some versions include a one-way check valve to equalize pressure when necessary, helping the system breathe under changing conditions.

• Threaded closure for secure seating and resistance to vibration
• Rubber gasket ensures a liquid-tight seal against contaminants
• Optional check valve for controlled air flow and pressure balance
• Direct fit for GM vehicles to preserve original tank performance

Will this cap reduce fuel vapor and save me trips to the pump?

By maintaining a secure seal, the cap minimizes vapor escape and the small fuel losses associated with an unsealed filler neck. That containment helps reduce unnecessary fuel loss and supports proper vehicle system operation that depends on controlled tank pressure.

• Sealed tank reduces hydrocarbon vapor loss
• Limits fuel evaporation for better fuel economy over time
• Helps maintain intended fuel system pressure characteristics

Is this the right replacement for my GM vehicle?

The GT329 (23368720) is a GM Genuine Parts item made to the same specifications as the original cap used on many GM vehicles. Confirm fitment using your vehicle’s year, make, and model or by comparing the part number to the one you are replacing to ensure compatibility.

• GM-recommended replacement part for original factory component
• Manufactured to GM OE quality, reliability, and durability standards
• Direct-fit design avoids modification or adapter requirements

How do I install and maintain the fuel filler cap?

Installation is straightforward: thread the cap onto the filler neck until it seats firmly and the gasket compresses. Periodically inspect the rubber gasket for cracking or debris and replace the cap if it shows wear to maintain the seal.

• Thread on until the gasket seats and cap is hand-tight
• Inspect gasket regularly for wear or hardening
• Clean filler neck and gasket area before installation to ensure seal

Who is this for: This GM Genuine Parts GT329 fuel tank filler cap is intended for owners, mechanics, and fleet managers seeking a factory-spec replacement for GM vehicles. It’s suited to anyone who wants to restore proper sealing, protect the fuel system from contamination, and maintain original equipment performance without aftermarket modifications. If your vehicle’s cap is missing, damaged, or failing to seal, this OEM part provides a direct, reliable swap that preserves GM-designed fuel system behavior.