The machines that measure the shear viscosity are measuring the oil in it's final formulation, so it seems like a valuable measurement. It's still a good comparitive parameter between oils if that's all you got. Notice in the chart Gokhan posted above that the HTFS is at a much higher shear rate than where the HTHS is measured at - a higher shear rate "fully aligns" the VII additives and therefore lowers the temporary viscosity. May only be applicable to certain moving regions in the engine (ie, rings, valve train)
Originally Posted by OilUzer
I now have a couple of big picture type of questions and/or issues: 1- Based on your info, I am thinking hths would be a useless parameter since its not a true representation of what's going on. So why is it published and/or talked about so much in the industry? 2- At the same time, I am thinking why would an intermediate measurement (htfs) prior to added vii be of a more importance than a final (after added vii) measurement? Basically it sound like throw hths in garbage No?