Do not add anything to the oil. The recommended oils meeting the dexos specification are all that is needed for good performance and engine protection.
Engine oil system flushes are not recommended and could cause engine damage not covered by the vehicle warranty.
Definition of Danger, Warning, Caution, and Note
The diagnosis and repair procedures in a GM Service Manualcontain both general and specific Dangers, Warnings, Cautions,Notes or Importants. GM is dedicated to the presentation of serviceinformation that helps the technician to diagnose and repair thesystems necessary for the proper operation of the ...