Isn't the powertrain warranty 60,000 miles or 5 years? If so, any Nissan dealer should be required to look at it. Would I assume thaty you did not buy it at a Nissan dealer? If not, find one quickly. Not sure how they will handle a used car that might have been abused - I am sure they will do their best to get out of covering it, but you have to start somewhere. My '03 has 84,000 on it, loses a half quart or so between changes and that is it. But I maintain it and while I drive it hard a lot, I don't abuse it.