The Oxford comma, sometimes also called the serial comma, is used to clear up confusion in sentences with lists. It’s really up to you whether you use it or not but for academic texts it can be useful. I prefer to use it as it just makes sure that you are being clear.
Take the following popular example:
We invited the strippers, JFK and Stalin.
Now, without the Oxford comma, it looks as if you are saying that JFK and Stalin are the strippers!
So, we would write:
We invited the strippers, JFK, and Stalin.
This makes it clear that JFK and Stalin have been invited as well as the strippers.
Not Always Necessary
It really depends on what you are writing though. Take this sentence:
We bought apples, mangos and bananas.
There’s really no danger of confusion in this sentence and so, if you like, you can leave out the comma before the final ‘and’ here.
Rejigging Your Sentence
You can also get around having to use the Oxford comma by simply restructuring your sentence. Our first sentence would be much clearer like this:
We invited JFK, Stalin and the strippers.
Generally, British and Australian writers are less likely to use the Oxford comma and certain American newspaper outlets also leave it out. Certain style guides may suggest its use or not, so check this to make sure. The best thing to do is to always ask yourself ‘is my sentence clear?’ If not, you might want to stick in a comma.