I'm an Oxford comma believer and am not going to try to convince anyone that it's correct, but here's an example from an article I just read that makes the argument for the comma. To understand the sentence, note the article is about basketball.
(Chris) Paul is averaging 14.9 points on 48.9% shooting, a league-best 10.4 assists and 4.5 rebounds.
Without the comma before the "and" it reads that he has a league best 10.4 assists and 4.5 rebounds. The 4.5 rebounds is what he's averaging, which is no way a league best. If the comma was there, that would be obvious.