Number 13 in diagram at link below? The one that goes around the filler kneck below the fill cap? (Fwiw, I don't think it does that much to seal anything.)
Gasket ring 11127526447

realoem.com is great for parts diagrams and numbers. Use the last 7 digits of your VIN to pull up your chassis.

 

Seems that not even realoem has it as that's the same part number for the gasket ring which seals the engine cover to the valve cover. You're probably right, it doesn't necessarily seal anything however it would help me sleep at night!

 

I think the o-ring is part of the oil cap. It's fairly important it seals, even if it doesn't let any oil out it will create a small vacuum leak.

 

The gasket is part of the cap. If you need the gasket then you have to buy a new cap.

 

I think you just need to replace the oil filler cap. I do not think you can buy that gasket.

 

I'd buy a piece of oil resistant rubber (silicone?) and make my own if it will come out of there. Likely just a circle? Oil filler cap could be cheap, though.

 

Yup. My last one was about 5 bucks from Reutter.

 

Not sure which seal you're asking about.

There's one as part of the oil filling cap. That's NOT sold separately.
Then there's a spill guard ring, that's part of the beauty cover. That one is sold separately.

Reutter is a great name in caps; oil, gas, diesel or otherwise.

 

I believe I am looking for the spill guard then. I am not looking for the gasket that is part of the cap. I am aware it only comes with the cap. Could you send a link for the spill guard?