I changed my 2009 Honda Civic EX Auto ATF fluid today. I did 5 drain and fills with OEM Honda DW-1 ATF. The car came with Honda Z-1 from the factory. The factory fill was pretty dark maroon. I didn't notice any abnormal shifting before the "flush" and I don't notice any difference with the DW-1 fluid in shift quality. It feels pretty much the same. I am glad I changed the fluid now though, as I know Z-1 doesn't hold up for very long. The car has 22k miles and I plan on doing the exact same thing every 20k from this point on. I plan on keeping the car for about 10 years, which would be about 200k miles for me.