Really. Recently scientists at Ohio State University dicovered the exact composition of tears, and its not just water - it includes oil.
What we think of as tears, scientists call tear film, which is made up of three distinct, microscopic layers. The middle, watery layer – what we normally think of as tears when we cry – is sandwiched between a layer of mucus and an outer layer of fatty, oily substances collectively called meibum.
It's in this outer layer that researchers describe, for the first time, a new class of lipids, or oils, that make up part of the film. They also identified one of these lipids, oleamide, which had not previously been known to be a part of tears.
With each blink, meibum spreads over the surface of the eye. It keeps the watery middle layer in place, ensuring that our eyes stay moist.
As a side benefit, the oil keeps your eyelids from creaking as they open and close ... just kidding about that.