Even though on many models you can use ATF in the steering, I still use steering fluid. It may cost a little more but there have been suggestions that the detergents etc in current ATF composition can harm the pump and/or steering box seals. Plus as an added benefit, when you have drips on the deck, it's easier to tell at a glance what is leaking. If your fluid had gotten black, you definitely need to change your steering fluid and filter.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.