The last time I did the change, I was curious of the viscosity difference. I made a basic draw down scale on a piece of sheet metal, laid down the same amount of new and used, and used a draw down bar to see how they compared. New compared to old 6K miles on the used. And there was no difference in the draw down. The only true diff I found was the viscosity weight. The used was 18% heavier by volume weight. Just a boring day the day I did this, not that it will help.
Ride safe all.
Greg