Which fluid should I use... the original one, or the "new" one that covers both the 722.6 and the 722.9 (seven speed)?
I have a few bottles of the 722.6 fluid around, but if the new fluid works better, I may switch.
Also, are both those fluids compatible (in case I get lazy and do not change the fluid from the torque convertor)?

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2008 S550
2010 GLK350
1997 E420 (retired)
2005 CLK500 (retired)