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I've recently purchased my first car (2004 Subaru Legacy), and though I sent it to the shop soon afterward for routine maintenance, I want to learn and do as much as possible myself. 3,000 miles have rolled by since then, and I'm sending it to the shop again to have maintenance done (and a few details checked on).

However, I changed the oil and filter myself today, so they won't need to this time. My question arises because in doing internet research before the job, I found that it's often recommended to change the oil drain plug gasket. So far so good. But the options stump me. So far I've heard fiber, nylon, rubber, copper, aluminum, and steel referenced. There are "crush washers". Some say metal is better, some say it's worse. Some say nylon melts.

My current washer is metal and seems in good shape. The contact with the pan and plug head is smooth, and the thread of the plug is very good. I guessed it would be fine to leave it in this time.

I want to do the best thing here, but I don't know what that is.

fassetar
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Daniel
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3 Answers3

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Assuming you're buying the OEM filter from a Subaru dealer, they should be giving you a new washer with each one. It's an aluminum washer that's sort of folded over on itself so that it crushes.

I just did an oil change, so here's a picture of the washers (used on the left, new on the right):

Used and new washers

Notice that the left one is appreciably flattened.

My understanding of the crush washer on your drain plug is that it's not a gasket -- i.e., not to keep fluid from leaking out -- but serves as a lock for the plug, and also as a mating surface between the steel of the pan and the steel of the plug, so that neither damages the other. Given that, and given that it deforms in order to fulfill its locking purpose, I believe it's best to replace it, and I'd suggest using the Subaru washer.

jscs
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I've been changing my own oil since 1975 or so, Daniel, more often than not, several cars at a time (it's been a long long time since I've only had one vehicle). I've never changed a drain plug gasket - I've never seen one that leaked significantly enough to warrant replacement.

Do wipe around the drain hole, and wipe the existing gasket, before putting the plug back in. That helps prevent dirt from getting in there & preventing a good seal.

EDIT: Oh, Crap. Subaru engineers in their infinite "wisdom" elected to equip that car with a real live crush washer, original is copper, domed side to the pan flat side to the plug head. They recommend replacing it at every oil change. Somehow that saves or earns them a little money, as compared to the nylon washer (if any washer at all) that everyone else uses.

If it were mine... I'd replace it (dealer price something like a dollar US each) only when necessary to make it stop leaking, and carry a couple of spares in the glovebox... and very seriously consider migrating to a nylon washer instead.

TDHofstetter
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I never had an oil pan plug leak until I got a Subaru. My 1966 Plymouth still has the original seal. Both Subaru leaked until I replace the crush seal. Buy them in a 10 pack and they are cheap. It does not matter whether they are steel or aluminum. Torque the plug to 31 lb/ft and live leak free. Subaru from 2004 forward have a bottom cover so leaks are not easily seen. Replace the seal and live trouble free.

J-PA
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