Power steering pump leak
 

When I was changing oil a few days ago I noticed that the bottom of the power steering pump is all covered in oil. I can't tell where it's coming from. It looks like the power steering fluid is dripping onto the engine oil pan (i.e., oil pressure switch), so it looks like the engine oil is also leaking at the switch.

Is there any way to tell the engine oil apart from the power steering fluid by looking at/smelling/feeling the oil from the stain on the ground?

what color is it? Steering fluid is usually dark red.. Check your level its a small canister on the left side.