There are "hydraulic fluids" used in the heavy equipment industry, and chances are they are compatible with MB power steering systems. Most are mineral oil based and have a viscosity in the range of a 10W motor oil or 70-75 gear oil like ATF.

ATF is formulated with some "friction modifiers" (like the additives for clutch or cone type limited slip differentials) for good wet clutch action and may also have some antioxidants to increase temperature degradation. All hydraulic fluids should also have some anti-foaming additives.

The trouble with MB and many other manufacturers is that they often don't give generic specifications, but say use part number... whatever, which are usually very high priced. The aftermarket is of little help since their products usually say "okay with most imports" or something similar, but don't say anything specific except for the fact that apparently Honda/Acura models require a "special" formulation, and some commercial power steering fluids state they are specifically for Hondas, while others specifically state not to use in Hondas.

Most automotive seals are neoprene based, which has good resistance to mineral oil and good temperature resistance up to about 200F, so I don't see how there is anything "special" about power steering seals or why Dexron III could be detrimental.

Since I want to change my power steering fluid and filter, I'm trying to sort this issue out, and there seems to be little other than hearsay and anecdotal evidence, however, these statements in the MB Service Products list clearly indicate that Dexron III is okay for vintage power steering systems, and I am hoping to sort out the issue once and for all.

Duke