To be clear: The Oxford, aka serial, comma, is a comma placed after the second in a series of items and before the coordinating conjunction. For example: bread, wine, and song. The comma after wine is a serial comma.
I used to have strong feelings about commas. Now, life just seems too short to get exercised about punctuation.
That being said: if you Google around, most say “Use it.” Just about every American and Canadian authority, style guide, whatever, uses it, except for newspapers and some magazines. Even in cases where they say “Don’t use it,” they qualify with “except where omission would cause confusion.” So, why not just use it and be done with it? That way you don’t have to give it any thought.
At least, be consistent. Avoid randomness. The best thing that can happen is that your reader is so caught up in what you’ve written that comma usage is invisible. If a potential donor starts noticing that sometimes you use it and sometimes you don’t, your message has been lost and your project has failed.
– Dinah O’Berry