Category A/B (2004) is combined for gasoline and light duty diesel engines.  Four subcategories show the A number followed by the B number followed by the year of implementation.  This category is for engines without after treatment devices. 

A1/B1 Oils for use in gasoline and car or light van diesel engines specifically designed to be capable of using low friction low viscosity oils with a HTHS viscosity of 2.6-3.5 mPa.  Sulfated ash 1.3% max.  Fuel economy test required.

A3/B3 Stable, stay-in-grade oil for use in high performance gasoline and car or light van diesel engines and/or for extended drain intervals where specified by the engine manufacturer, and/or for year-round use of low viscosity oils and/or for severe operating conditions as defined by the engine manufacturer.  HTHS viscosity of 3.5 mPa minimum.  Sulfated ash 1.5% max.

A3/B4 Stable, stay-in-grade oil intended for use in high performance gasoline and direct injection diesel engines, but also suitable for applications described under A3/B3.  HTHS viscosity of 3.5 mPa minimum.  Sulfated ash 1.6% max.