I was working on my truck and saw there was what seems to be engine oil all over the driver side of the engine bay coming from the Air intake. I took off the two main hoses that come from the top of the engine and found a third hose that is from the air filter to the engine oil cap.
One small hose about 1” thick from the air filter to the engine oil. Is this normal?
I’m not too familiar with this type or set up and it makes no sense to me that the air intake leads into the engine oil.
Any word about this would be appreciated thank you.

 

How is it running?
The engines PCV system by design pulls crankcase pressure combustion gasses into the intake to burn them off . The system also has a breather filter to vent/flow and aid the PCV, Without a breather filter, the PCV would quickly draw an excessive vacuum within the engine since the Its somewhat of a closed system. The breather filter helps manage and filter debris in the PCV flow.
If crankcase pressures are excessive due to engine wear, it can overwhelm the PCV and back oily residue out the air cleaner/box.. Or if the PCV itself plugged/restricted or its vacuum line same, meaning plugged at the manifold etc
You might check and make sure the PCV ops are spec, no restrictions etc..
Generally,, in a healthy PCV system, with the engine idling, if you remove the oil fill cap and place a business card on the fill neck flat area, the vacuum within the block should hold the card in place. If it won’t, or blow bye streams out the neck, either the PCV system isn’t working, or it can’t handle the amounts of internal pressure and then vents out the air box