Some of the reasons I don't care for Amsoil myself:

• Most of their oils are not rated by any outside group to any common standard, but instead are rated by themselves in house. Giving them a wide range of claims they can make for the oil with no independent analysis.
• Their business model is MLM, anytime you see something that depends on a dealer recruiting a dealer recruiting a dealer it gives cause for concern. MLM is not the same as middlemen either. Comp Cams sells to Summit Racing, who sells to you, thats a middleman, Comp sells a to Summit, who sells you a dealership for Comp, and you sell your buddy a dealership, who sells to his buddy a dealership, etc so you all get a cut from the end of the chain is MLM
• Anytime you see where someone has done an independent analysis of the Amsoil, if it comes out good, you see all kinds of comments from Amsoil reps that claims it shows how good the stuff is. IF, however, it come's out bad, the first thing you see is the same people saying it was a bad test, because it wasn't done using Amsoil's analysis service, and that it doesn't count because of that.

Bottom line, whenever I see the claims on how great Amsoil is, that Amsoil floods the internet with, I am reminded of the saying that "Ten out of ten dog's agree, dry dog food tastes like dry dog food"

And, FWIW, on a Cummins Sig600, there were no major differences in the oil analysis from it using Amsoil and their fancy filter, and my Cummins with the regular filter and Rotella.

Bottom line, while it may not be a bad product, until they step up to the plate and agree to have it tested by outsiders to show it meets or exceeds standards, I will stick with the ones who aren't afraid to test.

Oh, and one last thing, back in 2000 I was making a delivery at a place that packages oil into the little quart bottles. Their job was to take the base stock, add the additives, and then bottle it. While they were unloading, I was in the office of one of the guys who supervised the running of the machinery, and on his wall was a bunch of empty oil bottles showing all the brands they filled bottles for. I picked up a name brand bottle and a house brand bottle (I think maybe Castrol or such and a Wolfshead bottle) and asked him what the difference was between the two, his exact words "Mainly the container", when I asked him what he ran in his car, he pointed to the Wolfshead" brand.

My .02