I changed indy's when I got the '97 S320. They have been in business 40 years. Owner is German. I asked about transmission service. He explained that he doesn't use MB fluid. He uses synthetic fluid on the 722.6's. Claims he has had no problems.

I asked him whether he would stand behind that decision if my transmission went south. No, of course not, was his reply.

I had him do some suspension work on the car, but did the tranny service myself with the designated fluid. In my view, it's simply foolish to try and save a minor amount of money by second guessing the manufacturer.

Next service is due in another 40,000 miles, so I have a long time before the next one.
If I still have the car, I will go with the 722.9, backward compatible, fluid.

Steve