I thought I would go ahead post the ATF oil sample results from my wifes C230 because I know it's been a widely talked about topic on this board as to how often to change it so here are the results. Just a little background on this sample, it has 29,750 miles on it with a total of 60k miles on the car. I've changed the fluid and filter twice before this, once at 1500 miles and then again at 30k miles. The torque converter does not have a drain plug in it so at each change I get about 4L out of it. The first column are the actual readings and the second column is universal averages.

Aluminum 14/15
Chromium 0/1
Iron 48/107
Copper 76/109
Lead 11/25
Tin 4/5
Moly 0/1
Nickel 0/0
Manganese 0/2
Silver 0/0
Titanium 0/0
Potassium 0/1
Boron 87/83
Silicon 3/14
Sodium 4/9
Calcium 66/270
Magnesium 0/26
Phos 252/294
Zinc 4/112
Barium 1/64

Here are the comments from Blackstone Labs concerning this sample:

DALE: We didn't find anything unusual in this sample from your Mercedes' transmission. Aluminum
could be considered a bit high in relation to the other metals, but it's not high enough to show a
problem. We think this oil probably could have been left in place longer. No moisture or excessive
insolubles were present, and the viscosity was normal for ATF. No problems found.

It appears this fluid was in great shape and could have gone much longer. And of course for those of you that know my driving habits know that this car is not babied in any way when I get behind the wheel

What kind of ATF are you using? Anything special?

Mercedes spec ATF for 722.6 transmissions

I guess that's not totally true concerning the past fluids I've used in this transmission. At the 1500 mile mark I used Amsoil ATF and then changed it back over to the Mercedes spec fluid at 30k miles. So this sample is of the Mercedes spec fluid from the 30k mile mark to the 60k mile mark but I've used Amsoil in the past too.