Examination of lubricating oils by infrared spectroscopy

Approximately 60 oil samples obtained from the chassis of various motor cars have been examined by infrared spectroscopy. The samples were oils from the engine, gearbox and back-axle. Differences in absorbance of some absorption bands in the infrared spectra (IR) of oil samples were observed. An optimal set of absorption bands was chosen, which was used for quantitative comparison of slightly differing spectra. The significance of differences was tested using Hotelling's T²-test.