Description:

I've got three two (2) sets of two (2) different high temperature silicone o-rings for $10 including shipping if your oil filler cap is leaking like mine was earlier this year.  I also have o-rings for the coolant hose that connects to the bottom of the coolant expansion tank and for the N18 breather tube that connects to the valve cover on the driver's side.  If you want to add one of these onto your order, it'll be $2.50 each.  I will not be selling these separately.

I ended up buying a whole new cap from the dealership in February 2020.  Later, I went looking for a high temperature silicone o-ring for the oil filler cap because it seemed silly to have to spend $30 bucks on a new cap when the issue is the rubber o-ring.  After some searching, I found two good high temperature soft silicone o-rings from McMaster-Carr.

https://www.mcmaster.com/catalog/126/3725/

1. 1173N327 - Thicker
2. 1173N224 - Thinner

You can find the manufacturer specs by searching the page listed above using the model number.  I've been using the thinner one with the new cap for just under 600 miles and I haven't seen any oil leaking from it.

I'm selling one (1) of the thicker and one (1) of the thinner o-rings for $10 including shipping so you can decide which one you'd like to use.

If you decide to buy from McMaster-Carr directly, that's fine.  You might want to also pick up some o-rings for your breather valve, the one of the driver's side of the valve cover that points towards the front of car, and one for the hose that connects to the bottom of the coolant expansion tank.  Here are the part numbers.  I ended up replacing both; I noticed coolant was leaking when I moved the expansion tank during oil changes.

1. 1173N685 - O-ring for the N18 breather tube on the valve cover side
2. 1173N478 - O-ring for the hose that connects to the bottom of the coolant expansion tank

With the thicker o-ring, you won't be able to turn the oil filler cap all the way because of its thickness.  Also, you'll have to press down on the cap to compress the o-ring before you can loosen it.  I've included pictures below so you can see the difference between the two.

Picture #1 - Comparison picture.  Thicker on the left and thinner on the right.
Picture #2 - Thicker o-ring laid on top of a new OEM oil filler cap rubber o-ring.
Picture #3 - Thinner o-ring laid on top of a new OEM oil filler cap rubber o-ring.
Picture #4 - Thicker o-ring installed in an oil filler cap.
Picture #5 - Thinner o-ring installed in an oil filler cap.
Picture #6 - Thicker o-ring placed on top of oil filler hole.
Picture #7 - Thinner o-ring placed on top of oil filler hole.
Picture #8 - Oil filler cap fully tightened with thicker o-ring installed.  The thicker o-ring prevents the last 15 degrees or so of tightening.
Picture #9 - Picture of the N18 breather tube with o-ring installed at the top end.