91 yj oil soaked air filter

Hey fellas I just had the notion to check my air filter since I haven't checked it since I bought it a couple of weeks ago. When I lifter the top of the airbox the air filter looked more like an oil filter. I know this is usually a good sign of blowby, but is there anything else that would cause this? I have about 160000 miles on it but still, before I rip apart the engine I want to see if it is just a cheap fix, any Ideas?

Blocked PCV valve or over filled crankcase come to mind

i'm only heard of a blocked PCV valve and blow by. i didn't know an overfilled crankcase could cause that...