I could be wrong here, but it seems to me that the use of a crush washer is more about preventing the drain plug from becoming nearly impossible to remove, maybe not so much about preventing leaks.
I say this because on my 2010 Fusion, the first time I went to do an oil change, there was no crush washer on my drain plug, and it did not leak.
It was, however, almost impossible for me to remove. It was cranked down so tight, that when I tried to remove it using a standard socket and socket wrench, the head literally twisted and deformed but did not come out. In order to remove it, I had to hammer on an impact socket and use my breaker bar to remove it.
It was so messed up that this was the only way to take it off. I'm a little ashamed to admit it, but I continued using it for a few oil changes just like that, and was able to tighten it down sufficiently that it has not leaked once, even without a washer of any type. It always had to be tightened pretty tight, though.
It never really even occurred to me that it might need one until recently when I went to order a new plug.
I'll be changing the oil again in about 11 days, and I will be replacing the drain plug with a new magnetic one that I've bought, which includes a new crush washer. I fully expect that it will not need to be cranked down nearly as tight, and will still be leak-free.
)
