You sure its oil?
That is a heater hose and about the only thing that would be leaking in that area would be coolant. Its fairly common to leak from the bottom of where that hose goes into the fire wall.
From the looks of it,(mesh sock, spring clamps) its the original hose from 1991. Time to change them out and clean off the drippings. NAPA carries those hoses with the "s" curves in them.
I just changed out mine last weekend. Mine were OE (original equipment) also.
91 YJ Sahara, 4.0L, AX-15/NP231, D30/D35@3.07
12 Cherokee 4x4,3.7L,42RLE/MP1522, D30Mfirstname.lastname@example.org
"Non Vi Sed, Arte"