Welcome to the forum! Best is relative to individual preferences. What would be best for me is the Mopar locking gas cap that is keyed to my ignition key because I dont want another key on my key ring. Down side of that is they are about $80 if I remember right.
My wife bought me a locking door for the gas cap. Not sure of the technical term. It's flush with the body, once open it gives access to the gas cap. Knowing what I know now, I would have spent the extra money on the Mopar ignition key locking one. The one I have gives my wife and I fit at times to insert the key and unlock it. I think the cold has something to do with it, metal shrinking/expanding and such. Spend the extra $30 and get the Mopar one.
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