1) The current Amsoil 0w-30/5w30/10w-30 formulations are all ACEA A3/B3 rated and have been since the last reformulation. The qt and gallon containers show all the newest ratings - the website is just very slow to post the new spec sheets. The only one that is up to date is the 10w30, but the 0w30 and 5w30 meet all these same specifications. Since they are using a similar additive chemistry, this isn't surprising.
2) The Amsoil 10w-40 has been ACEA A3/B3 rated for the last several years, going back to the previous "SJ" formulation. The formulation works very well in modern gas engines as evidenced by the recent oil analysis results I posted for my Audi TT turbo. I honestly don't expect the xw-30 Amsoil formulations to do significantly better on wear rates or oil degradation. I ended up putting in the Amsoil 10w30 this time, so we'll see how that does.
3) Friction modifiers are normally added to help xw-20 and xw-30 oils meet the energy conserving rating that is part of the GF-3 spec. The xw-40 and xw-50 grades do not have to meet this specification. Typically the addition of an organic friction modifier like moly will provide approx a 1%-1.5% improvement in fuel efficiency.
4) The VI is a function of both the quality of the basestock blend and the VI modifier added. I would not assume that since the VI's of Amsoil are higher than the comparable Mobil 1 grades that they use much more VI modifier. Amsoil uses a high quality, shear resistant VI that I believe is sourced from Royal Dutch Shell - one of their "Shellvis" family of products.
5) The current additive chemistry Amsoil is using in their xw-30 oils DOES use less than 1000 ppm of phosphorus, for folks who angst about such things. I believe they made a conscience decision to do this, since the topic comes up from time to time on various websites.
6) I think Mobil makes very good synthetic lubes, FWIW. If I wasn't using Amsoil I'd probably be running Delvac 1, 5w-40 on a extended drain program.
TooSlick
Dixie Synthetics