Certified Lubrication Specialist Practice Test

Oxidation stability measures a lubricant’s resistance to oxidative degradation when exposed to heat and oxygen. When oils oxidize, additives can be consumed and degradation products such as acids, varnish, and sludge form, which can shorten oil life, increase corrosion risk, and impair performance. So, a lubricant with good oxidation stability resists these changes and stays effective longer.

Two common ways to assess it are induction time tests and monitoring TAN (total acid number) increase. In an induction time test, the oil is heated in an oxygen-rich, accelerated aging setup and the time until rapid oxidation occurs is measured; a longer induction time means better resistance to oxidation. Tracking TAN during aging shows how much acidic material is produced; a smaller increase in TAN indicates less oxidation.

Other choices aren’t about oxidation. Wear resistance relates to surface protection, not chemical aging; thermal conductivity concerns heat transfer; viscosity change with shear reflects shear stability, not oxidative degradation.