One of the washers fits the drain plug, at least in oil filters I got (not Mahle or Hastings).

Some manufacturers must supply bad O-rings, since I saw oil leaking from the cover of my 1985 when my son had it home. I found the O-ring very flat after just 1500 miles. Fortunately, I save the old O-rings (for other things) and had one that was still perfectly round. Sorry, I don't know the brand, but likely MTC or Champ since I have some in the garage and recall buying a group from rock cheap. Both "Made in India". They do have 3 copper washers in the box. India seems to striving for the bottom in quality.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans