… have switched to the Oxford comma.
The Oxford comma refers to the practice of including a comma before the final (or “penultimate,” for those of you studying for your SATs) word in a list, such as:
… dogs, cats, and fish.
It still looks wrong to me – I was taught not to use a comma with the word “and” – but my brother, who literally has a degree from Oxford along with lots of acronyms that go after his name, says it is the way to go.
Apparently, both are grammatically correct.
What matters in your writing, speaking, and marketing, in general, is that you remain consistent.