This is happening to my '97 Ford Ranger. Can someone tell me what is causing oil to seep into the air filter area? Someone told me its either a piston ring is faulty or the piston combustion chamber has worn out. If either one of these is the case, does anyone know about how much it usually costs to have it repaired? Thank you.

It should be nothing to worry about. it is most likely oil blow by from the pcv valve getting routed into your intake tube and it is slowly making its way to the air filter.

Do a compression test to confirm

I have 95 Mazda/Ranger with the 2.3 Liter engine and it has been doing the same thing. Replaced PCV valve about a year ago but problem seems to worse with the heavier motor oil I'm using now. Using about a quart or more every fill up now. Antifreeze and Oil both look good. Let me know if you figure it out.

you have to much compression in your engin block that's pushing oil thear, hope that help's

I would say pcv valve and possibly the pcv tube that goes around to the back side of your motor (the tube was a common problem on the Ranger and Explorer.