Originally Posted By: Jetronic
HTHS viscosity seems to be the first line of defense against wear.
Jetronic, yes, the initial fundimental of lubrication is to keep the parts separated, the ideal "zero wear" condition.
It's not a condition that exists in areas like the cam, lifters, and piston rings at the top and bottom reversal points, where the additives are in play.
As we move to a lower viscosity future, the additives come into play more frequently, and in more areas.
Originally Posted By: Jetronic
Note that the article only mentions bearing wear, and says nothing about ring wear which is more likely to send a car to the scrapyard
Rings are a bit more tricky, being hydrodynamic in the mid stroke (to the point that thermal barrier coatings are being applied to drop the mid stroke viscosity majorly), and heavily additive dependent at the ends of the stroke.