Anyone Else Use these Products? There seems to be an obsession here with Mobil 1. Obviously as it is an OEM recommended fill I can understand all the users. Royal Purple as I have run in my Camaro from its first 3,000 miles to know at 60,000 has been excellent. Every mechanic and racing insider I have spoken with have all pretty much said that Royal Purple is the best "stuff" out there. I have clearly noticed with Royal Purple: Fuel Efficieny gains of 2-3mpg highway, smoother idle and highway cruise. The hp gain of Royal Purple racing grades is also well known. As for AMSOIL? My SAE race team at the Univ of Texas use to run it. To our chegrin we stopped upon realizing that at least the then formulation of AMSOIL contained solids. Whether or not AMSOIL has now changed upon its recent API certification i do not know. As far as the K&N vs Mobil 1 vs AC Delco Ultraguard controversy for Best Oil Filter: It is my understanding that those the three filters are ALMOST the SAME THING minus brand specific features(end nut, burst strength). You can purchase the K&N at Jegs.com for only 9.99 By the way all 3 Filters are made my Champion Labs!!!!!