Agree that a loose gas cap is the #1 suspect. You could have gotten bad gas, but that would also affect the performance of the vehicle.

A gas cap needs to be replaced about every 5 years. But there are other possibilities. Go to O'Reilly Auto or a similar parts store they may be able to read the codes for you.

Gas cap most likely. Hooking up a scanner would confirm it.

Maybe your gas cap is loose?