got it out with irwin bolt and nut removers. Brill bit of kit.
You will have got swarf into the ird ,might be a godd idea to clean it out.
I hope you tried all the other options listed above.
I had totally fugked mine beyond all recognition.Tried vice grip ,lump hammer and cold chisel and maybe more ,before I decided to heat to almost red hot and old 17mm socket.
Then attached it to a 9"+4" extension bars.Then on my back I whacked the socket onto the filler plug from the end of the extension bar with my lump hammer , held the level behind the subframe
When it cooled (i think i DOUSED it with water) , I attached my ratchet and it came off easily with a very tight hold .
With the added bonus that I could fill the ird and drive to the dealer to get a new plug, with the old plug with new washer held in hand tight .
Jesus I did not want to have to type that way of doing this job again, because I have typed it here before , and keep seeing the same problems appear day in day out .
Just a simple scroll down the page might reveal that someone asked the same question half an hour or half a day before :doh: I might rant on .......
........:doh: