I am a strong advocate of the Oxford, otherwise known as the serial comma. It helps you avoid problems like the below:
I went to the store and bought firecrackers, razor blades, fertilizer, macaroni and cheese.
That sentence, at first glance, looks like I have purchased four things, because "macaroni and cheese" seems like one item.
But if I wrote
I went to the store and bought firecrackers, razor blades, fertilizer, macaroni, and cheese.
The extra comma after macaroni makes it obvious on first reading that those are two different things.
In short, it can't hurt, and sometimes it will make a sentence clearer. But you have to be consistent. Are you a free-wheeling, devil-may-care Oxford comma ignorer? Or are you a straight-shooting, clarity-seeking Oxford comma user?