I run royal purple in mine but it expensive as hell, but supposed to be one of the best. The thing I dont like about it is the only way you can tell it is starting to wear and burn up is buy smelling it because it is purplish black to begin with. I'll probably just go back to Mobile! synthetic due to the cost.
IMO I used royal purple in my 05 GTP. I had ALOT more done to that car and LOVED the royal purple. When I got the 07 I changed all fluid and added Royal purple. I went to have my oil changed before a road trip and it was about 500miles away from being 3,000 and the Tech guy asked when is the last time I changed my oil!! He said it looked as if I hadn't changed my oil in a good 6K miles! So im not sure if I got some bad oil or what. But I went back to Mobile 1 Syn. I know he was not bs'in me because he is my uncle! LOL.
Second, you can't just look at a synthetic oil to see if it needs changed.