Here's a easy mod for those of you who might be considering a locking gas cap. I installed a Motorcraft locking gas cap that looks just like the stock cap on my 2007 GT500. The part number is 8L3Z-9030-E. I had this cap installed on my car since January 2009 without any issue.





I pried off the button that secures the plastic strap with a plastic pry bar and popped the new one in place - simple!





The cap comes with two keys; I just keep one in the console so I don't have to carry it around.