I keep getting a check engine light.
When I put my reader on it, it says:
P0456 "Evaporative Emission System Leak-(Very Small Leak)"

The first time I saw it, low and behold, the fuel door wasn't closed. So I closed it and then reset the codes and all was well.
Then it came back but this time, I've been really watching to make sure the fuel door is closed.
About every few days, the code comes back even though I've been sure to keep that door closed.

I don't know if I'm doing something wrong or was supposed to service something. I have about 88k miles on the car.

Is there some history of this with this type or year of Mustang?

Is there a seal on the fuel door-gas cap that I need to replace?

Any info would be greatly appreciated,

Mike