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The reversible viscosity change of polymer-blended engine oils at low tempemtzcres depending on shear stress and on shear rate is vely cllamcteristic. This relationship is important for describing the 1ozu tenlperat~rre start(~bi1ity of engznes and the lozu teinperatzcre p7~mpability of engine oils.Tl~eJloui properties of polymer-blended engine oils have been iuvestigcrted. The inpzrence of several VI improvers, dijjferiizg in chemistry and in ~noleczrlar zueight, on the rl~eological prol~erties at slcbzcro temperat~tres zuns analyzed.In addition, a beizcl~ test zrsirig an engine oil prrmp 110s beef1 developed in order to obtnin low temperatzcre pzcmping duta on the test oils. The test established a better correlation between the effective vi.~cosity existing on the szrction side of aiz oil pztrni) and the pumping datrr than the correk~tion bctzueen the Cold Cranking Simz~lator viscosities or the porrr point and tl~ose pzcmping data.

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