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Reply to "Are Viscosity Index Improver Polymers all that bad?"

1. Consider your comparison of oil pressure and performance to be directly related, they simply is not necessarily the case. The oil pressure reading is directly related to the resistance that the oil pump experiences to work; a higher viscosity oil at the temperature that the oil pump is working in (80oC say) will normally give a higher pressure reading. It doesn't mean oil flow, just resistance to it. So your multi-grade may in fact be 'lighter' at the temperature of the oil at the oil pump, where the oil pressure sensors operate and then are converted onto the gauge that you see, giving you belief that oil pressure is lower, well in fact the oil flow may be better....

2. And what we don't get involved with, where we should, is the pressure/temperature co-eff. We look at viscoity under Full-film considerations, i.e. co-eff of viscoity for temperature, not the much more important EHL co-eff. which includes both temperature and pressure, important for ring areas, valve-train, etc. So looking at viscosity/temp charts all looks good, but what we need is the overlying pressure factors that really show how good the oil is at maintaining its composure (i.e. viscoity) when we load it up with something a little bit more weighted than 1G.
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