While spending/wasting time reading oil threads I ran into this. Bunches of details on M1 old vs new formula. Note the PDF is dated 2011, so I'm not sure if this is info on a proposed "new" formula or actually what they ended up reformulating to.
http://physics.usc.edu/Undergraduate...1-new-live.pdf
What I was looking for was M1 0w40 NOACK, which is listed as 9%. They also show a 3 hour test at ~24%.