http://www.valvoline.com/carcare/articleviewer.asp?pg=ccr20030601ps&cccid=2&scccid=1

According to this Valvoline document, Honda and Mercedes require a very specific type of fluid.

However, I read that some of the forum members use Valvoline P/S fluid. Doesn't it make trouble after long time?

I recently changed P/S fluid for my 1992 300D using Valvoline Synpower Power Steering Fluid.

The filler cap has no instruction about fluid, but it might have been peeled off. The owener's manual reads 1.1 US qt (1.0 liter) MB Power Steering Fluid.

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1992 300D 2.5 turbo diesel. 319 k miles.
124.128 chassis, 602.962 engine, 722.418 tranny.