At the end of the day synthetic motor oil is just that: Synthetic motor oil. It is base stock with different additive packages. It could be Amsoil, Mobil 1 or Toyota brand (which if truth be known is probably another brand labeled and formulated for Toyota) or any other brand. Sure, Amsoil might have minor differences in Magnesium qty or something but it is what it is: You personally might get a whopping 20% extra between changes but another guy with different driving habits or loads might get better with another brand. You said it right above when talking about analysis. It is engine lubricant. It does not feed the hungry children or cure cancer or make peace in the middle east. You are probably not going to race your 4Runner or enter it in any tractor pulls so peak performance is a non issue. Use the proper type and you will be fine as long as you use any of the well known brands.