Amsoil and synthetic are OK, (mercedes oil changes were at 50,000 miles on synthetic) but you still have to change your filter every 3 - 6000 miles.. SO you need an adaptor installed that will let you change your filter without draining all the oil at the same time.
Amsoil isn't supposed to reduce your oil changes, supposedly you can eliminate them, Amsoil advertises NO oil changes EVER, just top off with new when you check your level but you still have to figure out how to do the filter every 6k miles or so..
I'm surprised the environmentalists aren't all over this. Imagine the savings and the reduction of impact on the environment if there was NO used oil out there.. just used oil filters.
I run Mobil 1 in both trucks and the bike and change oil every 10K, mostly because of the filters, if I had the adaptors installed for the filters I think I'd stretch it to 25k..