My father has been able to use ATF in the powersteering pump in his Rolls, but then again its a GM pump anyway, and It has never been a problem in a pinch when he had a leak and needed to put somethign in there. After he fixed it, regular power steering fluid was always the best.

Now a benz is different, and I would hope that the Mercedes tech was only using mercedes or mercedes approved products in the car.

Alon

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'92 300CE - Sold
2004 C240 - 744 - C7 Wheels - Android Radio
2002 C320 - 816 - Sport Wagon - Sold
2006 E350 Wagon - 368 - Dead
2015 GL350 Bluetec - 197U