I asked the same question some time ago and could not find a satisfactory answer. BE VERY CAREFUL with using something not supplied by Mercedes, since it may not be compatible with the seals in the mechanism. I had to replace one of the hydraulic cylinders for $125 because it sprung a leak. There are six of them for the soft top mechanism. It would be potentially disasterous to put something in that would ruin the cylinders.

I had the original fluid analyzed and found it is a high quality hydraulic fluid. I ordered fluid from our forum sponsors, FastLane (MB Part No. 000 989 91 03 10), because I didn't want to take a chance with a fluid that may be incompatible. It's $17 a liter and is manufactured by Pentosin.

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95 E320 Cabriolet, 169K