Originally Posted By: LX289
VI Improvers are heat sensitive long chain, high molecular weight polymers that increase the relative viscosity of the oil at high temperatures. They work like springs, coiled at low temperatures and uncoiling at high temperatures. This makes the molecules larger (at high temps) which increases internal resistance within the thinning oil. They in effect "fight back" against the viscosity loss in the oil.
There's one problem with that bit of reasoning. Red Line uses as few VI improvers as is possible, this side of a monograde. So, if Red Line uses few to no VI improvers in their oil, how does that make the molecules larger? Additionally, VI improvers are far from the only (or even majority of) molecules in an oil. Motor oil is a compound, not a mixture. We're also comparing two oils with base stocks that are not identical, so the molecular size of VIIs is the least of one's worry here.
