I’m doing a series of ATF drain-and-fills. I get 4.2 quarts out of the 9.1qts capacity when I drain it (without removing the pan). After I refill, how many miles/minutes/starts-from-standing do I need to drive in order to fully mix the newly added ATF with the old ATF that remained in the transmission? I want make sure it’s fully mixed before the next drain, but I want to do the least amount of driving necessary.

So, can I just start the engine and go through the gears in place? Drive five minutes away on surface streets, then drive back? Ten minutes? How much gear shifting/warming up is needed before the new fluid is evenly mixed with the old?

Thanks!

 

Don't know.

Look at the fluid color as a sign of how well its mixed.

You can just start the engine and let idle. No need to drive, etc.

If your want an accurate fluid level on the dipstick check with fluid hot.

 

Correction: It looks like I get 3.8 qts. out (not 4.2) when I drain the ATF (don't trust the measurement marks stamped on containers).

I've done two drain-and-fills so far, and I calculate that I now have 2/3 new fluid, 1/3 old fluid (old means 60K miles). I plan to get it down to 1/10 old fluid. I bought a hand pump for the next drains.

I hope to never pay someone to drop the ATF pan and clean/change the (filter/screen?), and I'd like to avoid doing that myself. If I drain-and-fill to 80 or 90 per cent new fluid every 60K miles, what do you all think of that plan?

 

In my experience doing drain and refills never gets the fluid completely clear as the old fluid. The reason for this is the old fluid is being mixed with new rather then replaced. The color of the fluid is an indicator of fluid condition as used by mechanics including those at Toyota. Compare the color of the trans fluid with that in the container. Trans fluid color will range from dark to clear. The clearer the better.

A 80 to 90% change is good and its even better given this is being done at 60K miles. Most owners just do a single drain and refill or never change the fluid.