Under the hood of my 1999 E320 4-Matic wagon, I noticed a clear reservoir of "Center Hydraulic Fluid" (spelled Central Hydraulik). A few months ago, I noticed that the "CHF" was below the minimum line on the clear reservoir. The dealer refilled it to the max line, but what is this fluid (what automotive system does it apply to?) My 2001 E320 and 1998 E300TD do not have this reservoir. Has anyone else seen it (front left of engine bay in front of washer fluid). Thanks!