I went to get gas at the same Sunoco station I always go to. Instead of using 91 octane I put in 93 octane. I put in 3/4 of a tank. We were driving around and about 30 minutes later the gas light started flashing.
I stopped the car, turned it off and took off the gas cap and put it back on. We drove around for a bit and went home. A week later we were in the car and the gas light started flashing again.
I stopped and did the same as last time. I started driving and the light started flashing again and the check engine light came on. I took the car home and got codes P0455 & P0442 both evap leak codes.
I came on to the forum and did some searching and a few people had posted about their gas cap being the trouble. Luckily I still had my original and since I've put that on it hasn't hasn't happened.
I looked at both caps and the seal on the aftermarket cap looks like it's a tiny bit smaller than the original. Also the part number doesn't look right. The original also has metal guts as opposed to the aftermarket which has plastic guts.
That's why I'm pretty sure it's the gas cap.