I used to be a massive defender of the Oxford comma, now I think most examples where it adds clarity are usually the result of poor writing.
For example, “He met with his parents, the Pope and Barak Obama.” Is this a list of three people or are the Pope and Obama his parents?
All that needs to be done is to put his parents at the end. “He met with the Pope, Barak Obama and his parents.”
There are perhaps a few situations where it can add more clarity (a list of groups) but it’s hardly the saviour of English grammar some writers make it to be.