CARL explains.
Oxidation inhibitors, also called antioxidants (AO), are chemical additives which can slow or prevent reactions with oxygen and other oxidative processes. They are added to lubricants to delay ageing.
The BECHEM Lubricant ABC explains over 400 technical terms. On the web and with an app: http://www.bechem.de/en/service/abc-of-lubrication.html