Does anyone know the total fluid capacity of our '09 IS350 transmissions?

 

IIRC 350's get 8.3 qts RWD, 10.6 AWD. Its in the owners manual. That said its moot point unless starting with a reman trans with a new torque converter.

250's 7.9 qts RWD, 9.9 for AWD.

 

I need to know the total capacity because I want to do enough drain and fills till I get 90% new fluid.

 

If done correctly one could get 75/80% in three dump and fills. Even at that you would likely need like 12 qts.

Now if you are willing to get creative and say fit a pickup tube in place of the filter and feed the tube high volumes of fresh fluid you could likely do it with 10qts and get 95% of the fluid exchanged.

That said, once it starts mixing in the pan it it near impossible to get it all fresh. Best bet is drop drain plug and once its done Start it for 5 seconds. Remove the pan and filter. Let it drain. This will get you about 4.25 of the 8.5 qts. Now fill it, run it through all the gears once and repeat three times using 12qts and you'll be pretty darn close.

 

That's exactly what I did.
Pulled the pan, changed the filter, refilled with 3.5 to 4 qts (measured what came out) drove for 5 miles.
Did this 4 times reusing the old gasket until the last one then used the new gasket.
ended up using 14 quarts.
Dan