Application of dielectric spectroscopy for engine lubricating oil degradation monitoring

In this paper, Dielectric Spectroscopy (DS) was employed to analyze the oxidation degradation process of engine lubricating oil qualitatively and quantitatively compared with Fourier Transform Infrared Spectroscopy (FTIR). It was found that both DS and FTIR can directly obtain the degradation features from the spectral data. With the combination of DS and multivariate calibration (Partial Least Square PLS), three main oil monitoring properties including Oxidation Duration (OD), Total Acid Number (TAN) and Insoluble Content (IC) can be determined quantitatively and accurately. It was proved that operating temperature had more influence on DS data than excitation amplitude. The results in the article show that DS can be developed into an effective oil monitoring/analysis method.