Last week I took my Murano (2004) for a regular oil change to the Nissan dealer. On the comments section of the receipt, they have noted the following: Please use Octane 93 to reduce the engine knocking issue. I never reported any issues and I didn't notice my Murano 'knocking'. I didn't look at the comments section until I came home. I only use octane 89 for Murano but 93 for my 350Z. What do they mean by this? Any help/input is appreciated.