for the past two time I pump gas, I noticed an overflow on my gas tank. normally when I fill the tank, the pump automatically stop itself when the tank is "full", but recently, it just keep on filling until gas gushes out of my tank like a fountain.

this happen at two different gas station so I dont think it the pump, so it could be my car. Anyone here familiar with this?

 

It's the car, but you can make any pump with a working cutoff actually cut off. When you first put the nozzle in, make sure that the pump actually cuts off with a full pull. If not, take the nozzle out, reinsert, and try again until it works.