I recently purchased an 84 Vanagon with a 93 Subie 2.2 that a PO installed.

The engine has good compression (180-185 all around) runs well,
sounds nice, lots of power etc.  The top of the engine is clean and
dry, the bottom of the timing belt covers are a little oily.

I just went on an 800 mile drive.  At the end of the drive, the rear
hatch was covered in a thin film of what appears to be motor oil.
Even the license plate and rear window were covered in this oil.

Has anyone seen this?

Could the engine be leaking oil and by some sort of 'Venturi effect'
it is getting sucked onto the rear hatch of the van?  Or is the oil
coming from somewhere else?