I did not realize that 30-weight is used on all Honda since 2006, it must be the oil availability issue causing this not popular in other continents since the thin oil can survive in tropical heat.
http://world.honda.com/environment/report/download/2010/2010_reportdata_E_05.pdf
http://world.honda.com/environment/report/download/2010/2010_reportdata_E_05.pdf