There are a variety of polymers which the industry uses as VII. Country of origin is irrelevant. They all differ in cost and performance (ie. shear stability). Different grades meeting the same specification may require more or less or a different type which may cost less or cost more.what do you mean? differences between us and european vii's of the same oil? i could be.but i can think of one right now.have an example?
Viscosity index improvers include polymethacrylates (PMA), polyisobutylene (PIB), radial polyisoprene and olefin co-polymers (OCP)*.