0W 10W 15W What additive did they add ?

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Hi guy, I don't find someone talking on this (Or maybe I missed some post). I have a question about "W" number. As we know that it was rated for low temperature viscosity and I don't need to care about this number if I live in hot country. But, I would like to know what kind of chemical/additive they add to lower W number. And if they add it. In my opinion, it should be something that affect oil characteristic at high temp too (Or not?). It might look too serious to choose an oil but I'm new to this role and would like to learn about this.
 
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The winter rating is affected by the base oils used, viscosity modifying polymers, and, to a degree, pour point depressants. For instance, two oils of similar high temperature viscosity where one is a PAO and one is a conventional oil, the PAO based oil should have a lower winter rating than the conventional because of the base oil characteristics even before viscosity modifiers or pour point depressants are added. That is the basic gist of how it works for the most part, but there are more subtle mechanisms that effect the overall result too.
 
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Viscosity modifying polymers and pour point depressants are indeed the biggest reason why there is a large spread between the numbers on conventional oils (non-synthetic) Synthetic oils can behave differently, depending on the formula or blending. Amsoil offers a "straight 30W" that is also rated at 10W-30, just because of it's chemistry, and not necessarily because of additives.
 

taoybb

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Thanks for reply and info. I'm just looking on Torco SR-5R and they have two option on 50 weight, 5W-50 and 20W-50. Let say if on track, which one would be better to go ?
 
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Pour points of -39C for 5W and -40C for a 0W? Those numbers don't look right to me. That being said, the 5W should theoretically give you better engine efficiency due to less parasitic losses at temperatures below 100 centigrade because of the lower overall viscosity at those temperatures.
 
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Originally Posted By: MotoTribologist
Pour points of -39C for 5W and -40C for a 0W? Those numbers don't look right to me. That being said, the 5W should theoretically give you better engine efficiency due to less parasitic losses at temperatures below 100 centigrade because of the lower overall viscosity at those temperatures.
Note that the CCS results for the 5WXX oils are reported at -25C and CCS for the 0WXX oil is at -30C...5C higher than the SAE definitions for the grades. Something is very strange here. That said, I would probably go with the 20W50 if I lived in a hot place like Thailand.
 
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