"Hydraulic" oil

[Robert Phillips <r3rfp@dax.cc.uakron.edu>]

I have been thinking about this for quite some time.

I have an 87 4000S, 1.8L

The cap on the power steering says ATF.

The reservoir says "use only mineral oil"

I know the 5000 series uses the Pentosin hydraulic stuff, but some of the 
4K's use ATF (dextron,etc.) and some use Pentosin.  I plan on draining 
the fluid and changing the filter in the reservoir soon for normal 
maintenance, but don't really know what to put back in.  I feel that I 
can't rely on what the previous owner has installed, so I appeal to the 
Gods of all Audi's for advice.      What gives????
			-------Bob