The Xfire manual calls for 5w-20 meeting API SL or GF3. I believe the current stuff is a non-synthetic oil. Some dealers may replace it with full synthetic to help fix a notchy tranny. I don't know if there is an overfill bolt hole on the side of the tranny but I sure hope there is. I plan on changing mine every 50k miles, I don't care what the book says, no tranny in the history of cars has every lasted forever without fluid changes. Metal shavings are inevitable over time.