A method for experimental determination of the temperature intervals of structure formation and the activation energy of viscous flow is described on the example of lube oils. The results obtained are interpreted from the point of view of nonequilibrium thermodynamics.Lube oils, whose quality significantly affects the reliability of operation of machines and mechanisms, are considered to be complex colloidal systems. In contrast to true solutions, multiphasicity and internal heterogeneity are characteristics of such systems [1]. Intermolecular interactions of different intensity take place in colloidal solutions, as in real solutions. As a result of these interactions, micelles, supramicellar formations, associates, and liquid-and solid-crystalline structures arise as a function of the external conditions and temperature [1,2].The behavior of colloidal solutions when the temperature of the system decreases is of special interest:the mobility of associates decreases sharply due to strengthening of their internal bonds and the appearance of new bonds. Based on the practical importance of such behavior, we will analyze the process of low-temperature structure formation below. The physical analysis of the behavior of such complex multicomponent systems as petroleum disperse systems (PDS) can be performed statistically by introducing the concept of the average current energy of the intermolecular interaction in a liquid in given external conditions X:In practice, structure formation in PDS is usually investigated by viscometric methods [3]. However, these methods have a number of drawbacks, and the fundamental ones are:• usually use of an exponential dependence between the structure-sensitive parameters of a liquid (viscosity, conductivity, dielectric constant, etc.) [4,5] that characterize its structural transformation in certain conditions and the reciprocal of the temperature of the liquid; theory and experiment show that this extrapolation only holds in a narrow temperature range, outside of the region of strong structural changes [6]; • use of rotary or capillary viscometers for determining the viscosity, which causes mechanical destruction of the structures;

A c o m p re h e n s i v e s t u d y o f t h e r m o s t i m u l a t e d m i c ro s t r u c t u r a l p ro c e s s e s i n l u b e o i l s b y t h e simultaneous use of three independent physical channels for obtaining information on theseprocesses -optical, vibro-viscometric, and thermographic -is described. A simultaneous change in the signals as a function of the temperature in all three channel s was experimentally demonstrated. The dependence of the intensity of the microstructural processes on the cooling rate and composition of the lube oil was confirmed. .Lube oils of different functional application are widely used in the most diverse areas of human activity.Improving their performance properties is directly correlated with making their composition more complicated. This makes it necessary to constantly perfect methods and agents for assessing their qualitative composition to ensure the maximum effectiveness of their use.It was demonstrated in detail in [1] that modern methods of analysis are being increasingly actively used for studying the disperse structure of petroleum systems, but the limited possibilities and complexity of these methods have significantly impeded finding the quantitative correlation of the macroscopic properties and microstructure of petroleum disperse systems. Nevertheless, current advances in science in physics, synergetics, colloid and physical chemistry, petrochemistry, and computer technologies for processing large masses of experimental data already allow investigating some correlations between the macroscopic characteristics and microscopic properties of lube oils.We previously [2] investigated microstructural processes in lube oils by vibroviscometry and described a method of investigating intermolecular interactions in lube oils by methods of nonequilibrium thermodynamics with automated computer processing of the viscosity -temperature curves obtained.We experimentally confirmed the existence of microstructure in lube oil [2], using additional independent physical channels of obtaining information -optical and thermographic.