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Here is a picture of my gas cap. This is what is on my gas tank that has no vent nipple. It says "Anti Surge" above the tabs and says "Vented" below the tabs.

Is this cap meant to let air in and out?? Or just let air in as the fuel level drops?



That sure looks like a pressure-vacuum cap. It will let make-up air in unrestricted, and let air out (pressure from expansion) out once a predetermined PSI / KpA is reached. I guess it can fail like anything else mechanical.

It is normal to hear a "whoosh" when removing it.

It is unusual to see one of those without the second set of bayonet tabs, which are designed to keep the cap from hitting you in the face. Maybe first year for the design?

Rick