Hi,
I have now changed the oil for my 240s, 740, 940s for 20 years or so. Never changed a copper washer. Don´t have any problems with leaks. Would neber use any kind of goo that could get into the oil! I re-use the old coppert washers. Hand-torque with the wrench set T-bar as hard as I can (I am a fairly muscular but still office-worker, would that be 140 lb ft???). What I take care to do is let the oil drain out for 10 min. Then I wipe the surface clean, where the copper gasket should do its sealing job. Whatever little grain that is left there will of course cause a leak! When it is time to change oil again, one will always need the T-bar and something hard to punch it with to get the plug loose. AND: in this European car you still have to realize that the drain plug needs a 1" socket. A 25 mm just won´t work! Don´t ask me why this is so. This valuable info I got from a friendly mechanic, we all rely on them, don´t we. Many thanks to those who contribute!

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The only other washer that I have seen for a drain plug was a crush washer. I would probably still over tighten that too.

This is how I was educated:
There is a reason why I over tighten drain plugs and it is not because of drips. I had a drain plug vibrate out on a family trip in a Ply Voyager years ago. I must have forgotten to tighten it, but I'm NOT totally convinced I didn't. A very Good Samaritan VA State policeman saved the day by bringing a gallon of oil and a Ford drain plug which cross threaded nicely, considering.

BTW, what is the proper torque? Couldn't find it in the Hanes book. Maybe I don't over tighten.
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Tom F

I always have a tube of silicone caulk that I use for sealing up the drain plug on my son's 82 GLT. I find many uses for it and many times don't even have the tip in place (it is one of those large tubes with a removalable tip). I simply unscrew the plug and squeeze out the small amount needed. It is great stuff and with it and things like dental floss, epoxy, heat shrink tubing, etc I repair a lot of things that would otherwise be tossed.

Randy

My car will leak from the oil drain plug even if it is very tight with a new copper gasket. I use an o-ring at the base of threads on the oil drain plug. It does not leak. If you use an o-ring is too large it won't work. You need one which will sit down in the tapered area leading to the threads in the pan.

Ideally you would find a washer that would keep the o-ring from pushing out from under the edge of the drain plug hex. I intend to do that, but I haven't gotten it yet.