Sythetic Oil has helped me alot, but my car still turns over slow when it gets cold. After reading another thread the other day I finally figured out that if I clean some of the contacts around the starter it might help. I havn't done that yet, but I am hoping it will. If that doesn't work, then that means that I need a new starter. I am going to say that if Synthetic oil doesn't help, then try you might have some bad contacts, or need a starter.