Quote:
Originally Posted by rice_classic
Sorry b.e., not trying to rain on your parade but what you state is a common misconception about oil rating. Thanks for your understanding.
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Thanks for setting me right. I've done a bit more work on the problem, and have found that the difference in the viscosity index numbers has some bearing on the
b parameter of the variance of viscosity with temperature, viscosity= ue^(-bT) It's not a direct bearing, however.
The trouble, I think, is that the SAE defined two different indices for the cold and hot numbers. Dumb but true. 20W-20 is not a single-grade oil. Oils for other uses have their own indices, also. Alas, science and mechanics do not mix.
I'll fix my post above.