GM GENUINE PARTS fuel tank filler cap GT330 (20915842) — direct-fit replacement with rubber gasket for leak-free seal

GM Genuine Parts GT330 (20915842) is an original-equipment fuel tank filler cap designed to restore a secure, leak-free seal for compatible GM vehicles.

Replacing a worn or missing fuel cap is a quick, low-cost way to maintain fuel economy, control vapor emissions, and keep contaminants out of your vehicle’s fuel system. The GT330 (20915842) cap is built to GM specifications and uses a resilient rubber gasket and pressure-management features to perform like the factory-installed component. It’s intended as a direct-fit replacement that preserves the durability and fitment standards expected from GM Genuine Parts.

How does this cap keep fuel and contaminants out?

The GT330 relies on a molded rubber gasket to form a liquid-tight seal at the filler neck, preventing fuel seepage and blocking dirt and water entry. Some caps in this design include a pressure-check valve to balance tank air pressure during normal use, which helps protect the tank and fuel system.

• Durable rubber gasket for a secure, fluid-tight seal
• Precision fit to the filler neck to stop dirt and moisture
• Check-valve feature manages internal tank pressure when equipped

Will the GT330 fit my GM vehicle and replace the original cap?

This part is a GM-recommended replacement engineered to match the original equipment specifications for compatible models. Fitment depends on your vehicle’s year and fill-neck design, so verify part number 20915842 against your vehicle’s service or parts catalog before ordering.

• Manufactured to GM OE dimensions for direct replacement
• Matches factory performance, durability, and service life
• Check vehicle compatibility using VIN or parts lookup

How does a sealed fuel cap help with emissions and fuel economy?

A tight-fitting fuel cap minimizes vapor loss from the fuel tank, reducing evaporative emissions that contribute to smog and waste. By keeping vapors contained, the cap also helps prevent small, continuous fuel losses that can slightly lower fuel economy over time.

• Limits evaporative vapor emissions for environmental benefit
• Prevents slow fuel loss and unnecessary refueling stops
• Supports proper operation of the vehicle’s evaporative emissions system

What should I inspect when installing this replacement cap?

Before installing, inspect the filler neck for corrosion, debris, and any damaged sealing surfaces to ensure the new cap seats correctly. Replace the cap if the rubber gasket shows wear or if you experience a check-engine light associated with evap system leaks.

• Clean filler neck of dirt and fuel residues
• Check gasket for cracks or compression set
• Confirm cap threads and latch engage smoothly for a secure fit

Who is this for: The GM Genuine Parts GT330 (20915842) fuel tank filler cap is ideal for owners of GM vehicles who need an exact-fit replacement to restore original sealing performance. It suits DIY mechanics, service shops, and anyone wanting to maintain OEM standards for durability, emissions control, and fuel containment. Always confirm compatibility with your vehicle’s parts reference or VIN before purchase.