how to explain this?

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Jan 7, 2003
Havoline Synthetic 5w-30 pour point of -44F, Hav. Synth 5w-40 pour point of -60F. 5w-30 flash point of 471 f. 5w-40 flash point of 432 f. I was under the impression that the higher second number would allow a higher flash point? And why the significantly improved pour point on the 5w-40? Could it have something to do with viscosity improvers? The VI on 5w-30 is 172 vs. 158 on the 5w-40. Mikep
Originally posted by Dr. T: Do you think the stats reversed for the 2 grades?
I'm almost afraid to even take a guess at why the stats could be what they are. But here goes anyway. Could it be the 5w-40 contains PAO or esters thus improving the cold pour point. Then since PAO or esters are in use, they didn't feel a need for as many vis improvers in the 5w-40 thus the lower VI vs. the 5w-30. Would that then explain the lower flash point? A lower VI would mean less shear stable at high temp? I'm getting way out of my league here even taking this guess. What do you think Dr. T? Mikep
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