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)?

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

What production date is on the car? You could just use regular ATF, and not the expensive kind. But if it is the special stuff, it is computer controlled and the computer will alwase adjust shift pressures to make it shift nice. But he problem is the bearings and races in the trans. Doesn't matter if you change the fluid or not, they are defective, so around 80-100K you will be puting a trans in it, and making sure the computer is up to date. I reccomend this site. We do alot of buisness with them and they are better and cheaper than factory. They put better parts in the trans, and are up to date on everything! I would not reccomend anyone else. Here is the link. www.peterschmid.com Really should replace the fluid in the converter, if you get tired of waiting for the fluid to drain, loosen the 19mm size banjo bolt on the drivers side. Just crack it and turn it once or twice.

My car is a 1997 E420 with the "fill for life" 722.6 synthetic fluid....

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

didnt know their was a seven speed fluid...however, at a minimum you must use the Mercedes ATF.
Dont use off the shelf ATF or you will have problems.

The ATF used in the 722.9 will work in the 722.6. I don't know if it offers any advantages over the original ATF.

Yes the fluids are different. But if you are having problems with it, just drive it because a filter/fluid change wont help.

The 722.9 fluid will work in 722.3,.4,.5 and 722.6 cars. The cost of the fluid is somewhere around $25 per liter. That's an expensive service! I'd go with the MB 722.6 fluid.

The "fill for life" motto is now outdated by serveral MB service bulletins in which they "advise" to change the fluid on 722.6 transmissions.

The local dealer here don't "advise" you to change the fluid, they "insist" to do it, before the 722.6 will destroy itself.

__________________
A. Rosich
CL 500, 1998
S 500 L, 1998
E 320 T, 1995 [Sadly sold ]