Stovebold,
Interesting thoughts. My only comment is that after 6000 miles, it's a crap-shoot as to the condition of the test sample. If this sample didn't pass the 'pregnancy test', it would be a firm testament to changing your oil at 3000 mile intervals.
You are right about the VI improvers 'shearing'...that's what they are suppose to do. The part that was left out is that they (the molecules) repair themselves..this happens over and over until the oil is 'worn out'. This is when the ability to 'multi-vis' is gone...probably by the time you tested your 6000 mile oil.
There are several reasons why you change your oil at the suggested interval. One reason is the oil is 'full'..it has trapped and held all the contaminants it can and it needs to be changed. The other reason is that it is worn out...it is 'sheared to death' and offers little lubrication in those high stress areas like cam lobes and piston skirts.
This is how I understand this black magic.
Stuart
