I can tell you I was a RP guy for many years until the costs skyrocketed, I guess to support the advertising. Have been using Mobil 1 for a year but just switched to Amsoil in the Cobra tranny due to a great local Amsoil rep and this thread. Will most likely switch to Amsoil for all my vehicles since it is so readily availalble here. My question is "Why Does the Amsoil trnasmission fliud smell so bad and does the engine oil have the same smell"?