AT drain and refill...percentages?

kannibul

I have a Honda Civic, and it has a 12 quart system.

I drained and refilled 3 quarts of ATF today.

I plan on doing another drain and refill next weekend since I over-filled by probably 1/2-1/3qt.


So, here goes:

Since the old fluid and the new fluid will mingle, that means I have 75% old fluid swimming in my transmission.

Now I take another 25% from that, by drain and refill.

So, I could assume that I need to do 12 - 25% - 25%?

If so, then that means I have 6.75:5.25 old:new = 56.25% old fluid?

Then if I does it once again, that'd be 12 -25% -25% -25% = 5.0625:6.9375 old:new = 42.1875% old fluid?

Am I on the right track?


Thanks!