The analysis of engine oil or other lubricant for the purpose of identifying premature component wearing has been performed for several decades using optical atomic spectroscopy (e.g., atomic emission spectroscopy (AES), as well as atomic absorption spectroscopy (AAS)). This technology was the basis for the military aviation's Spectroscopic Oil Analysis Program (SOAP). However, it has certain disadvantages, such as a lack of repeatability among different equipment and an inability to analyze particles greater than 5 μm in diameter. Furthermore, optical atomic spectroscopy is an elemental analysis of the total oil sample and typically does not characterize individual particles in the sample.
Other approaches have since been proposed, whereby individual particles may be characterized and classified based on their chemical composition. However, these approaches are not sufficient to predict complex component failures.