The OP is going to have a very difficult time getting any real help here. One problem with this website unfortunately.
You have brand bias by all, because all have an "experience" to share. Then you have vendors "Pablo" and others that sell the products (only giving out his name since he responded to the OP post). I would not dismiss what they say right off, but if they are selling the product?? There is bias.
I have used so many oils over the years. The bottom line is, Amsoil is no better than other oils and vise versa. Its all marketing, and any "Tests" are all subjective by use and motor and we can go on and on back and forth on this for days.
I will say it again. If you go to wallyworld and lets say your car takes 5qts of oil for example. You just want to follow your car manufactures recommendations and change your oil every 5k-7500 miles. You go to wallyworld and buy M1, Castrol Edge, Valvoline, Penzoil ANY of these over the counter synthetics that can be bought for allot less than any Boutique brand oil and your engine will last literally forever. You just cant beat wallyworld for pricing on the oil. It is what it is like it or not. I hate wallyworld, but their oil is just the best pricing out there.
To say, if you use Redline, Amsoil, Motul or whatever is going to make your car last longer and give you more HP or more MPG's is all marketing hype that marketers go on for days to debate so they can sell you their product.
Bottom line? Follow the manufacturers recommendation for oil type, many dont even say to use a synthetic oil, but if you do use one, and its the spec you need and you follow the oil change interval of the manufacturers your car will last a very very long time. Who knows your engine better, than those who made it?
OP, Hope this helps you.
Jeff