Bear in mind that when we replace ATF, its not a complete drain because much of the ATF is lock up in the torque converter chamber.. the common method of ATF replacement is only draining whatever left on the tranny oil pan and replace it with fresh ATF. The next time we run the gearbox, the fresh ATF will be drawn into the torque converter chamber and mix with the old ATF to somewhat dilute the dirty ATF into less dirty ATF.. therefore, the more frequent we replace the ATF, the better because the ATF in the tranny gets less dirty. I know some actually do it every 20k km.. to keep the ATF "red"..
My Toyota is every 40k km.. factory recommended. Every time I DIY the replacement, I tend to over fill it a little (+250~500ml), then I siphon the excess out from the dipstick outlet, after running it for some time.. I noticed whatever siphoned out remain dark red in color like undiluted Ribena compare to the transparent red ATF that pour it..
Stupid tranny design!! :stupid: