INVESTIGATION OF MOTOR OIL DEGRADATION BY FLUORESCENCE METHOD

Abstract

This article presents a study aimed at developing fluorescence spectroscopy as an express method for diagnosing the condition of motor oil, which can serve as an alternative to standard laboratory analyses.

The work investigated the degradation of synthetic motor oil using fluorescence analysis and acid number determination. Fluorescence spectra were measured with a FluoroTest fluorimeter, and the acid number was determined by potentiometric titration with potassium hydroxide. The analysis used samples of fresh oil and used oil after the car had traveled distances of 180, 430, 720, and 910 km.

It is shown that with increasing mileage, the fluorescence intensity decreases, and the ratio of peaks at 584 nm and 610 nm changes, indicating structural changes in the oil’s composition. The results revealed that the acid number of the oil increases with mileage, which points to its oxidation. A motor oil degradation coefficient (K_dmo​) is proposed, defined as the ratio of the intensities of the mentioned peaks, and which increases proportionally with the acid number at the early stages of use. A linear correlation between the acid number and K_dmo​ was established for mileage up to 500 km (R²=0.9913).

The obtained results confirm the feasibility of using spectroscopic methods in conjunction with titrimetric analysis for the rapid assessment of motor oil condition and the control of its operational characteristics.