You can read the conclusion at the end of the executive summary. They only studied xW-20 and xW-30. As I pointed out, they found that friction modifiers only make a small difference.
Regarding viscosity, the precision of their tests were not sufficient for a statistically meaningful conclusion but then they didn't study any xW-40 oils. I also see a similar result in real life that there is not a whole a lot difference between 0W-20 and 5W-30 but a lot if difference with 15W-40.
Regarding viscosity, the precision of their tests were not sufficient for a statistically meaningful conclusion but then they didn't study any xW-40 oils. I also see a similar result in real life that there is not a whole a lot difference between 0W-20 and 5W-30 but a lot if difference with 15W-40.