If you run Amsoil and run it 15-20k between changes just remember that most likely your warranty won't cover any issues since you aren't following the recommendations in the manual...
I don't know where the manual tells you about oil changes, I just wait for the computer to tell me when. The oils that we have today are good enough, you don't need to pay a bunch of money for synthetic. The computer tells you when to change oil, due to your mileage and driving habits.
I really doubt that Amsoil will save an engine over regular maintenance with standard oil, and the thought that it needs changed every 2-3000 miles is not true.
