Regarding to the importance of increasing combination of the viscosity index in the efficiency of lubricants, articles titled "Study and comparison of shear stability index of polymers that increase the star viscosity index used in engine oil" by Mr. Amir Hossein Saghafi, engineering expert of Afzon Ravan Company, was prepared and accepted by the 11th International Conference of Internal Combustion and Oil Engines.
The summary of this article can be found at the website of conference in the following address:
http://www.iranengine.com/paper?manu=40614
Also, in order to read this article, you can visit the following address:
http://www.afzoonravan.com/upload/download/1583931209.pdf