Gene,

This is usually an indication that the front main seal of the engine is
leaking. This is the seal at the point where the crankshaft comes out
of the crankcase.

It is not as bad as it sounds, as long as you get it fixed promptly.
If you leave it, it will often get worse quickly. Then you will think
it is raining (droplets on the windscreen). Shortly after that...
well... how are your off-field landing skills?

Gene Hudson
CFII, ASC