Ok, this seems simple.
I've looked for this in my manual, did a search here and looked at new ones and I still can't find out what size socket to use. I swear I've seen this somewhere, but now when I need it I can't find it. I've used a 20mm and it wants to slip. I don't what to guess again and make it worse.
I don't know how long it's been since this has been removed as I just got the car and it's my first oil change on a 12a.

thanks,
Stan

 

Stock is 19mm. If the PO installed an aftermarket, it can range from 17mm to 15mm to 14mm.

 

Cool. Thanks for the quick response!

I tried the 19 and it seemed too small. The PO might have buggered up the head though and if he replaced it I'll have to try something else...

thanks again,
Stan

 

Can you tap a 19mm wrench or socket on it? It has probably been boogered by the PO.

 

That's exactly what I ended up doing. The end was a mess! I put it back on until I get another one...

thanks.