ANALYSIS OF DEPOSIT FORMATION CAUSES DURING MOTOR OIL LONG-TERM STORAGE
Modern high-efficient motor oils are widely used in vehicle maintenance. These oils are produced by Russian and foreign manufacturers in large and small vacuum-packed containers. When motor oils are purchased by customers often the only way to evaluate their quality is the visual determination of color, transparency and presence of sludge in the container. Therefore, sedimentation in oil is common cause for its rejection by consumers. The mechanism of deposit formation in the commercial oil may vary. The most frequent causes of its formation are: - precipitation of polymer viscosity modifiers during multiple cycles of cooling and warming during winter storage; - precipitation of oil insoluble part of additive package; - precipitation of water in the form of turbidity (emulsion); - mechanical impurities from contamination of oils during production, storage and packaging. Due to the fact that, in contrast to standard assays of fresh oils, there are no regulated procedures to determine the causes of sedimentation, in the research laboratories the methods of analysis for each case of deposit formation are selected at the discretion of chemical engineers and technologists, making it difficult to compare with previous results. The aim of this work was to develop a common method for analyzing the causes of deposit formation in the oil, since the rapid determination of this cause will facilitate the timely troubleshooting and product quality improvement. It is shown that to detect the type of sediment and the causes of its formation range of methods can be used, including the separation of the sample, the determination of its water content and filterability, elemental analysis of the original oil and sediment after its separation. Use of this method complex is demonstrated on two samples of commercial oils with different types of sludge that were returned by consumers.