My old roommate used to swear by RP. I personally havn't used RP. I have used Amsoil in my old truck and loved it. I'll be making the swap over to syn. soon. Just need to let the motor break in a little longer. Also found some links.
http://www.royalpurple.com/video/video.html
http://neptune.spacebears.com/cars/s.../oil-life.html