An in-service lubricant encounters air, heat, pressure, corrosive agents, and other factors that cause chemical changes in the oil. A change in oil chemistry can affect the ability of the lubricant to do its job (for example if crucial additives have been depleted). Over time, these chemical reactions can result in build-up of harmful degradation by-products like weak organic acids. Oil chemistry analysis always includes oxidation and may also include nitration and sulfation depending on the application. In some cases, oils may also be tested to check for the depletion of specific additives, like a ZDDP antiwear package.
Testing for oxidation, nitration, and sulfation of a lubricant allows trending of useful oil life and can also signal improper operating conditions, failure of engine parts (piston seals), or the wrong lubricant for the application. There are indirect methods of testing lubricant’s ability to perform its function, like viscosity, but the only direct method to determine whether oxidation, nitration, or sulfation is happening is to use infrared spectroscopy. FTIR instruments and methods are available for intermediate to expert users in a laboratory setting and the Spectro Scientific FluidScan allows testing for oil chemistry out in the field (or in the lab) with a portable IR spectrometer.
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