Oil oxidation is quantified by using Fourier Transform Infared Spectroscopy or "FTIR" and looking for the presence of carbon-oxygen double bonds, called "carbonyl" groups. The three major species formed by oxidation - Aldehydes,Hydroperoxides and Carboxylic acids, all contain these carbonyl groups. This class of compounds will typically absorb infared light in the 1740 abs/cm region. By looking at the amplitude of the peak in that wavelength, the extend of oxidation can be determined.
Lubes such as Redline and the Series 2000/3000 formulations can generate inaccurate FTIR data, unless the machine has been specifically calibrated with an unused sample of the oil. I speculate what's happening is an ester component of the basestock blend is absorbing light in the 1700-1800 abs/cm range and throwing off the FTIR calibration.
The best way to tell if the oxidation # is real is to look at changes in viscosity and TBN. If viscosity is close to the baseline value and the TBN is high, then a high Ox # is mainly calibration error.
As an informational note, the by-products of nitration absorb infared light in the 1600-1640 abs/cm range, so the extent of nitration can also be quantified using FTIR. Both oxidation/nitration are "inversely proportional" to TBN, ie as they increase the TBN drops ....
TS
