Guys I'm buying this jeep today. Dont really know the history of oil changes. It's not even had 3k put on it in over a year. It currently has 197k miles on it. Sounds awesome and in perfect shape inside and out. What weight oil should I put in this 4 cylinder? I was going to put in synthetic oil but I've read it may start leaking oil. Well it already has a small leak nothing major at all.