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Springer Science+Business Media, Inc.Polymeric V.I.(compounding) improvers are an inherent component of a major part of modern motor oils. They impart required viscosity-temperature characteristics to the oils, and thereby permit their successful use at both ambient-air temperatures, and also high engine-operating temperatures. In the first case, polymeric V.I. improvers provide for required starting properties and pumpability of the oils. And, in the second, ensure the development of the required oil film that separate contacting components, minimizing their wear in turn.In conformity with accumulated experience, polymeric V.I. improvers are selected, as a rule, on the basis of regulated viscosity-temperature characteristics of the motor oils. Here, the behavior of these improvers under high-temperature catalytic action on the oil, which is typical of operating conditions, remains beyond the purview of researchers in a large number of cases.Focusing attention on the practical significance of the problem in question, it was studied in an example of three ethylene-propylene polymeric V. I. improvers, two of which were foreign products -samples A and C, and one a domestic product developed by the OOO NPP Kvalitet -sample B.The study was conducted for the purpose of assessing possible behavioral characteristics of domestic compounding agents as compared with the behavior of typical foreign commercial prototypes, which are in widespread use to produce motor oils of the highest operational groups.Two bases were compounded by the indicated polymers to produce motor oils of the viscosity classes SAE 10W/40 and SAE 15W/40. The level of the operational properties of these oils, which correspond to groups SG/CD and CF-4/SG in accordance with the American Petroleum Institute (API) was achieved by adding to the compounded bases packets of similar improvers for each group of oils. Use of monotypic packets of improvers was dictated by the need to equalize the influence exerted by packets of some functional purpose on the effect of the polymeric V.I. improvers.One of the bases selected for compounding was a petroleum oil (to produce an oil corresponding to SAE 15W/40 and CF-4/SG in accordance with the API) and the other a mixture of petroleum and synthetic (poly-á -olefins) oils (to produce an oil corresponding to SAE 10W/40 and SG/CD in accordance with the API).