Floppy Subaru Gasket
This bulletin applies to all 2011 and later Subaru vehicles equipped with FA or FB engines. If the fuel cap sealing gasket has come loose, remove the gasket and inspect/clean for any dirt or debris.
Clean the gasket and the gasket groove in the filler cap. Reinstall the gasket into the receiving groove until fully seated, with the tapered lip side of the gasket facing the cap threads. The square side of the gasket must face upwards, fully seated into the cap groove.