We don't use Oxford commas, also known as serial commas. An Oxford comma is when you use a comma in a list before the word "and".

For example, it should be: "I went to the beach with my dog, Auntie Jill and David". Not "I went to the beach with my dog, Auntie Jill, and David".

You can use a comma before "and" if the context isn't a list, and it will introduce a new clause or break up a long sentence.