Light absorption spectra for lubricate oil quality tracking in the combustion engine

The important role in the proper functioning of combustion engines plays the quality of lubricates oil. However, the quality of oil changes with the time of exploitation. Therefore, several parameters for examination of oil quality were determined; however, the indicator for quick and efficient tracking of evolution of oil with exploitation time is still searched. Taking into account the complex composition of oils, the ability of oils components to absorb light in various wavelengths is considered. In the article absorption properties of oils is discussed in relation to the time of circulation of oil in the engine lubricate system. For this study, two lubricate oils designated to lubricate the cylinder of vessel engines with different brightness and transparency were used. Oil samples were dissolved in organic solvent –n-hexane and several oil concentration were prepared based on dilution method. Absorbance spectra for eachsamples of oil were registered in the range of wavelength 240-600 nm. Obtained results indicate the changes of value of absorbance in relation to the kind of oil; however, the shape of absorbance spectra is independent from the kind of oil. For studied kinds of oil, characteristic peak independent from the kind of oil located at 260 nm was determined. Based on Lambert-Beer law absorption coefficient was identified as a potential indicator to oil quality evaluation with the time of exploitation in the engine system. Preliminary test for two fresh lubricate oils allow to conclude that absorption coefficient for selected wavelength located at 260 nm could be a sensitive parameter for quick estimating the degree of deterioration of the oil in engine system.