PAO vs Dino VI golden information

[wulimaster]

I ran across this site and thought everyone would be interested. Here is a link to a graph on the differences of two VHVI basestock oils which have the same VI. One oil is a pao and the other is non-synthetic. Their other web pages contain very valuable information also. From what I gather, a 15w40 pao should outperform a 5w30 dino at very low temperatures. The VI index is only a measure of the viscocity of an oil between 32 degrees F and 212 degrees F compaired to 2 base oils which are assigned a value of 100 and 0 respectively. Here is the link. Enjoy. http://www.cpchem.com/pao/products/hiviscosityindex.asp

 

[nicrfe1370]

wulimaster, That is one great resource. The more I learn about synthetics, the less likely I am to ever use anything but synthetics or even group III oils.

 

[Ken2]

wuli, Viscosity index is calculted between 40°C and 100°C. "To access this property of a lubricating oil the American Society for Testing and Materials (ASTM) created a method to provide a number called the Viscosity Index (VI) which correlates the amount of viscosity change for a given oil compared to two reference oils having the highest and lowest viscosity indices at the time when the VI scale was first introduced (1929). A standard paraffinic oil was given a VI of 100 and a standard naphthenic oil a VI of 0. Tables have been prepared which show the relationship between viscosities at 40 and 100°C. The method has been updated and revised several times to include VI values higher than 100. "The important thing to remember is: a low VI means a relatively large viscosity change with temperature and a high VI denotes a smaller change of viscosity with temperature. Hence, the VI of an oil is of importance in applications where an appreciable change in temperature of the lubricating oil could affect the start-up or operating characteristics of the equipment." http://www.fammllc.com/htmlpub/LUBE_bulletin_06.htm Also see "viscosity index" @ http://www.chevron.com/prodserv/NewOronite/library/li_dictionary_v.htm A 15W- oil of any composition must have a viscosity no more than 7000 centiPoise @ -20°C. A 5W- oil of any composition must have a viscosity no more than 6600 cP @ -30°C. So...by definition, if the oils are correctly labeled, the 5W- oil is thinner when cold than the 15W- oil. As your link says, "...PAOs require fewer VI improvers [to achieve the desired viscosity index] and are less likely to create performance-limiting deposits." Ken

 

[wulimaster]

quote:

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Originally posted by Ken2: wuli, Viscosity index is calculted between 40°C and 100°C. A 15W- oil of any composition must have a viscosity no more than 7000 centiPoise @ -20°C. A 5W- oil of any composition must have a viscosity no more than 6600 cP @ -30°C. So...by definition, if the oils are correctly labeled, the 5W- oil is thinner when cold than the 15W- oil. Ken

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Sorry Ken2, I was thinking of two statements and combined them into one sentence. What I was hoping to point out was what happens to synthetic versus group III,II,I oils as they approach temperatures much below 0 C which is only 32 F. A good 15w pao could outpump a poor dino 5w below -25C. If you look at the graph of identical weight and VI basestock group III and Group IV oils you can see what happens down where it really matters. http://www.cpchem.com/pao/faqs/faq1.asp If this graph is any indication, then a 15w PAO won't be significantly thicker at temperatures around 0F to make much of a difference to cold engine lubrication. Plus the fact that PAO's tend to provide a thin film of oil longer on engines that are shut off for extended periods of time.