Mine did the same thing.
I went to WalMart and got those little round (silver) magnets from the crafts section and some epoxt glue from the home improvement section.
it was all around $10 I think.
I took the fuel door off (2 screws) laid it on a flat surface and just epoxied the magnets to the outer (away from hinge) corners.
Let it dry for an hour and put the door back on.
To open it now I just push on the hinge side edge.
Doesnt open in the wind, on the freeway or at the car wash anymore.
Quick, cheap and easy fix.