Well, if you are serious and realy want it out, I would try applying a bit of heat. I have successfull used a heat gun. It woll take a few minutes maybe five or ten but it will get HOT. You can also use a propoane torch or bottle but I like to save that for the really tough ones. Then It is hammer and chisel time. It will come out and you need a new plug anyway. Get the new plug, get the old one out and then drain teh lubricant. This is a reasonable common problem especially in norherrn climes and where the previous owner did no maintenance for the last 15 years.