![]() These SHEAR STABIL 0w-40 oils do a great job as Factory fill lubricants around the world Why Ted? Can't you sleep at night? If we changed it to sheer stability would you feel happier? ![]() You worry so much about 0w-40 synthetic lubricants and shear stability. However, it does tell you how "squeezable"the oil is, which reflects the polymer content.Īll things being equal, the more polymeric thickener, the more likely the lube is to shear in actual service. The high temp, high shear test done 150C does NOT cause a permanent loss of viscosity (as does the multi-cycle, Bosch Injector test). For those of you who are engineers or materials scientists, this is roughly analogous to elastic deformation of metals, ie "Hookes Law". As the rubber flows between the roller, it is compressed and then it snaps back to its' original cross sectional area on the other side. The best way to visualize this is to think of what happens when you run a piece of rubber between two steel rollers. The HT/HS test uses a tapered bearing simulator and the oil flows through it under high pressure and temp.Īs the oil flows through this restrictive bearing orifice, the long chain polymers align themselves in the direction of flow, hence the oil temporarily thins out. The reason why SAE 0w-40's perform so poorly in this test is directly related to their high polymer content.
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