I found out something interesting about my 05 Escape XLT. I bought it used so I've very new to it.
I still have to get the whole story from the guys at the Ford dealer parts counter. I'm getting the story second hand.....I asked my wife to order a locking gas cap and they told her I can't get one.
The parts guy looked up my VIN. Apparently, on my particular Escape, I can't use a locking gas cap, even one from Ford. Something about a return line or vacuum that a locking gas cap won't address and will lead to CEL coming on.
I'm going there tommorrow to get the story.
Hopefully, you can get a locking gas cap for your Escape. I wanted one for mine for the same reasons.....prevent fuel theft and vandalism. | 
