Patman posted a good topic a while back regarding Viscosity Index: http://theoildrop.server101.com/ubb/ultimatebb.php?ubb=get_topic;f=1;t=000002#000000 Now, Bob explained the "meaning" of Viscosity Index pretty well, IMHO. However, I still think that Patman's question was left unanswered:
quote:Let's pick on Mobil SuperSyn for example. 0W40 has the highest VI of 185. Could it be that 0W40 has a high inherent VI, OR did it have the same VI as the others (5W30, 10W30) and Mobil decided to inject a huge amount of VII? If it is the latter, wouldn't the VII be less reliable and more prone to "disappear" since it is just an "additive". I hope I made some sense. Comments? Oz
Or does having a higher number not necessarily always equal a better oil?