Dino,
Check out: http://www.infineum.com/information/tables.html,
they have all the ACEA sequences there.
Here's the quote for A5/B5:
"A5/B5 Stable, stay-in-grade oil intended for use at extended drain intervals in high performance gasoline and car + light van diesel engines designed to be capable of using low friction low viscosity oils with a HTHS rate viscosity of 2.9 to 3.5 mPa.s. These oils may be unsuitable for use in some engines. Consult owner manual or handbook if in doubt."
Regards,
paul....