How to Buy an Oil Sump Drain Plug or Washer

My daughters car had an oil leak. Luckily for me, the leak was coming from the oil filter housing. An easy fix, a new filter housing oil seal (often supplied with a new filter). The car needed an oil change, so I went ahead and drained the oil…

The original oil filter housing leak was fixed, but now the sump drain plug was leaking and I couldn’t get it to stop!

Oil Drain Sump Plug & Copper Washer

What did I do?

Well, the shops were shut, so I dug around in my box of washers (for a sealing washer). They were all too big or too small! I was scratching my head what to do? I needed to get it fixed. I had some old copper pipe. So I used this to make a new washer. I fitted the homemade copper washer to the sump plug. It partly worked, but there was a very slow leak. It would do whilst a found a proper replacement…


How to Fix a Leaking Oil Sump Drain Plug?

There are a few options you can take. Replace with:

A New Oil Sump Drain Plug:

A straightforward like for like replacement for your old oil sump drain plug. Just make sure it comes with a new sealing washer.

  • Most oil sump drain plugs have sealing washers. If yours was one that didn’t have one fitted, you may want to consider fitting one?
  • Make sure you have the correct size and type (socket fitment) for your needs. A parts supplier should be able to advise…

A New Oil Sump Drain Plug Replacement Washer:

There are several different types of sealing washer…


A copper washer is the most common type of sealing washer for oil sump drain plugs. They say to never reuse sealing washers, but the copper sealing washer will probably survive reuse better than most.

  • Copper hardens with use. Therefore it may not provide such a good seal second time round...
  • You can anneal (soften) copper, by heating till it’s pinkish red and leaving to cool naturally, (or quenching in water).

Copper (Crush Type):

A copper crush type sealing washer provides a good seal but must not be overtightened. They should only be used once, as the one time crushing action provides the seal.

Dowty Type (Metal & Rubber):

A ‘Dowty’ type of sealing washer is often used for high pressure applications, for sealing gases, oils, and other fluids. They are made out of various metals incorporating a rubber type seal.

Dowty type sealing washers will wear quickly if reused and retightened.

Nylon (plastic):

A nylon type of sealing washer has low friction and can withstand various chemicals. Nylon (particularly Nylon 6/6) can withstand high temperatures. Nylon also has ‘adsorption properties’, which allow it to compress providing a seal.

They should probably not be reused if they become overly compressed or deformed.


A fiber washer is great for many applications, such as oil sump drain plugs. They can compress to provide a seal, plus they have the added ability to absorb fluids. Absorbing fluids has the benefit of allowing the washer to swell slightly, thus providing a better seal. They must not be overtightened.

Fiber washers will wear quickly if overtightened, or re-used.


An aluminium sealing washer is similar to copper, but is softer. It is therefore able to compress and seal slightly easier, but will wear more quickly than copper.


A copper sealing washer is probably the pick of the bunch for oil sump drain plugs (for wear and tear). However, the other types will probably form a better seal, but wear more quickly. Having to be replaced after every use.

When it’s Not the Washer…

There are a few options you can take.

  • If the oil sump drain thread is worn or stripped, you can buy a new oversized sump drain plug that cuts a new thread when inserted and replaces your old drain plug.
  • You can use a Helicoil.
  • A sump drain plug repair kit.
  • A new sump.

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Oil Drain Sump Plug & Copper Washer
Oil Drain Sump Plug & O’ring
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