Sheesh!
The length of the Wall is 493' 6". It would take a pretty stupid person to "accidentally" squirt (or dribble, or spray, or pour, or dip one's hand into a bucket of some unknown oily substance and flick handsfull of) stuff onto the Wall for 493' 6".
Grounds crews, and presumably electricians to maintain the lights, run the full length of the wall on a regular basis. As I mentioned in another post, the grass at the top of the wall in the first picture looks freshly-edged. If that granite is anything like my granite counters, they periodically reapply sealant to protect the stone from the elements.
I’m thinking the stream from an oil can would have sufficient pressure to reach a greater height than the damage visible in the photos.
This looks like a gravity fed stream, like what might be produced if someone walked along with the tube from a Camelback hanging out of their sleeve. The up and down pattern would be consistent with a swinging arm motion produced while walking.