Identifying and modelling changes in chemical properties of engine oils by use of infrared spectroscopy

Abstract

The aim of this paper was to describe the interdependencies between the surface areas of characteristic FTIR spectral bands, reflecting the amounts of chemical substances generated during oil deterioration in engine, and the mileage of the cars depending on the oil used. The tested engine oils were used in 12 similar vehicles operated in similar conditions and an attempt was made to describe the differences between the kinetics of changes in the groups of investigated oils and, likewise, to provide a possible explanation of their causes while examining the relationships between individual spectral bands. Based on the areas of spectral peaks, a mathematical model, characterizing engine oil deterioration: Y = β ₀ + β1 ·X + β2 ·X2 + ε was developed. Based on the MOB algorithm, a total of 10 functional models describing the key chemical changes depending on the mileage were determined. The obtained findings suggest that the type of engine oil differentiates the changes in the surface area of the spectral band at the wavenumber 860 cm−1, 1150 cm−1, 1270 cm−1 and 1710–1760 cm−1, depending on the car mileage and using a given oil.