The 3 top oils according to lab analysis after usage are
German Castrol
Redline Synthetic
Amsoil
Mobil and Royal Purple performed poorly compared to these other oils. The German Castrol is the cheapest of the group and works the best. It's only 5 bucks a quart. You can tell the German apart form the regular cause it has a green label on the front instead of red, and in the back it says "Made in Germany" and "approved for Porsche" somewhere in all the clutter. If you wanna know more about oil, check this website out.
http://www.bobistheoilguy.com/