So just an update, my 2018 CX9 GT is at 171k kms or so. Noticed my fuel economy slip way down from 7.0L/100kms to about 12L/100kms.
At the time of this change, I had about 165k kms. The last I changed plugs was roughly 120k, not quite the 64k mark as per the manual. My first change was done at...