when switching from a otc synthetic (mobil 1, syntec, etc) to amsoil would there be any special considerations? amsoil says when going from dino to amsoil to do an amsoil engine flush if it has some miles on it and to do a shorter interval at first (i think, may be wrong), so would this apply to cars that have some miles on them that used synthetic as well? my car would have 50000 or 60000 miles on it at the time of switch and has had synthetic oil its entire life.