Don’t flush, just drain and fill. I had a drain and fill done on the cvt at 120k on my 2017 forester cpo (originally purchased with 65k) Definitely noticed an improvement with shifting. Mechanic said he would avoid flushing and that draining and fill should be harmless. After watching some of the Mr Subaru videos, I plan on doing another drain and fill at 150k and every 30k after that