SSO is nearly gone, a few DC's have a little on hand. All new orders will be filled with AZO.
I would not say the SSO was downgraded, the AZO, ASL, ASM are all API SN, ISLAC GF5. ASL is dexos1 so they all have been upgraded.
Quote:
04-07-2011
Signature Series 0W-30 (SSO) Unavailable for Online Ordering, New Signature Series 0W-30 (AZO) is now available for purchase online, by phone and at all AMSOIL Distribution Centers.
Quote:
The expansion of the Signature Series family required a repositioning of the 0W30 viscosity to ensure uniformity throughout the line. All four oils now have similar packaging and each now carries a 25,000 mile oil drain recommendation, which serves to eliminate all confusion for Dealers and customers. The 25,000 mile oil drain recommendation aligns with today’s engine technology modifications, including smaller oil sumps, more closed combustion systems and more challenging engine operating conditions.
Quote:
AMSOIL 5W30 (ASL) meets the recently released GM dexos1™ specification, as this is the viscosity it recommends, and AMSOIL 0W30 (AZO) is recommended as a replacement viscosity for dexos1™.