This is what I would use if I owned a Wasserboxer.

>ENGINE OIL: 20-50w (Brand?)

15-40 year round, except 20/50 during a heat wave. Changed by inspection,
not time or milage.
Any quality brand will do. I prefer Valvoline, because it is available in a
great many private labels in any burg and typically at low cost.

>OIL FILTER: Mann or Mahle (Bosch?)

Mahle

>COOLANT: Halvolene Dex-Cool (phosphate-free, ethylene glycol based,
>Orange), Blue Stuff? (what is it? who makes it?)

Phosphate free e-glychol, any brand will do. The new Dex Cool meets this
spec. It only took Detroit 40 years to get up to the speed of the Euro cars
of the 50's. Complete system drain, rinse, renew every year.

>MAN TRANS OIL: ??
>(for syncro, if different)

Valvoline 85w-90 GL-3/4, changed by inspection, not by time or miles.

>AUTO TRANS FLUID: ??

Dexron III for the gears, GL-4 for the differential. Changed by inspection,
not by time or miles.

>BRAKE FLUID: ??

DOT 4, renewed yearly.

>POWER STEERING FLUID: ??

Dexron III, changed by inspection, not by time or miles.