4b8cf347_ations___oilspecifications_org__Service_Gasoline_Engines
["S"] SM [Status] Introduced on 30 November 2004 [Service Gasoline Engines] 
Category SM oils are designed to provide improved oxidation resistance, improved deposit protection, better wear protection, and better low-temperature performance over the life of the oil. Some SM oils may also meet the latest ILSAC specification and/or qualify as Energy Conserving. They may be used where API Service Category SJ and SL earlier categories are recommended.
API Engine Oil Lubricant Specifications - oilspecifications.org
Service Gasoline Engines