IP 157: Determination of the oxidation stability of inhibited mineral oils (the TOST test)

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  • Method adopted/last revised: 2018
  • Method reapproved: None
  • REF/ISBN: IP157-7250659
  • Status: Current
  • First printed in STM books: May 2019


This standard specifies a method of evaluating the oxidation stability of inhibited turbine oils, hydraulic oils and circulating oils having a density less than that of water and containing rust and oxidation inhibitors, in the presence of oxygen, water and copper and iron metals, at an elevated temperature.

Note 1 The procedure is widely used in clause 7 is for carrying out a life test. See annex B for the procedure for carrying out a 1000 h test.

Note 2 This method is widely used for specification purposes and is considered to be of value estimating the oxidation stability of lubricants, especially those that are prone to water contamination. It should be recognized, however, that correlation between results of this method and the oxidation stability of a lubricant in field service can vary markedly with field-service conditions and with various lubricants. The precision statement for this method was determined on turbine oils only.

Note 3 A significant tendency to form insolubles under these oxidizing conditions can indicate oxidation of the oil, or corrosion of the metal catalysts, or both. Insolubles can indicate operation problems; however, no correlation has yet been established with field service.

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