Www.bobistheoilguy.com
/thread

If Honda dealers in Florida, US (which is Townsville weather) safely uses 5w-20 in Hondas and Acuras, why would I want to use something that's 2.5 times as thick. Honda engines aren't detroit V8's, we don't have as much tolerances in there.

Thicker =/= better
Bitog forums has plenty of oil test results that shows that.