The big concern is, obviously, spillage when filling up. There's also a risk that a radical temperature swing could cause the fuel volume to expand, causing a full tank to spill over without the driver knowing about it. According to the National Highway Traffic Safety Administration bulletin, if the fuel spills over, it could end up in something called the charcoal canister, which helps with the car's emissions. If it fills up the canister, it could leak out onto the road. None of this is really desirable.
The affected vehicles were all built between October 25, 2012 and May 9, 2013. It's unclear if there have been any fires due to this problem. Dealers should have been notified by now, while owners should begin receiving official recall notifications very soon.
To remedy the issue, dealers will install an adapter in the fuel tank's shutoff valve and, if necessary, replace the charcoal canister. Naturally, the repairs will be handled free of charge.
Take a look below for the notification from NHTSA.
Mazda North America Operations (Mazda) is recalling certain model year 2014 Mazda6 vehicles manufactured October 25, 2012, through May 9, 2013. In the affected vehicles, it is possible to fill the fuel tank beyond its rated capacity.
If the tank is overfilled, gas may flow into the charcoal canister (an evaporative emissions component) and possibly leak from the canister's external vent, increasing the risk of a fire.
Mazda will notify owners and dealers will inspect and add an adapter to the shut off valve in the fuel tank and also inspect the charcoal canister for the presence of gasoline, replacing it as necessary, free of charge. The recall is expected to begin in late April 2014. Owners may contact Mazda at 1-800-222-5500. Mazda's number for this recall is 7414D.
Owners may also contact the National Highway Traffic Safety Administration Vehicle Safety Hotline at 1-888-327-4236 (TTY 1-800-424-9153), or go to www.safercar.gov.