http://www.carbibles.com/engineoil_bible.html
The full ACEA specs are:
A1 Fuel Economy Petrol †
A2 Standard performance level
A3 High performance and / or extended drain
A5 Fuel economy petrol with extended drain capability †
B1 Fuel Economy diesel †
B2 Standard performance level (now obsolete)
B3 High performance and / or extended drain
B4 For direct injection passenger car diesel engines
B5 Fuel economy diesel with extended drain capability †
† Not suitable for all engines - should ONLY be used in engines specifying this fuel efficient grade. Refer to the manufacturer handbook of contact your local dealer if you're not sure.