Oil in the filter is because the engine is breathing (normal). What sounds abnormal is the quantity - dripping onto your driveway it shouldn't be. So the engine is breathing harder than it should be.
"Breathing" is where exhaust gasses pass the piston rings into the crankcase (happens in all engines, even brand new ones). If your rings are shot, this is exasperated and "heavy breathing" occurs, dragging more oil into the breather system than normal. In a closed system (the standard inlet system) this is generally trapped in the intake and recirculated into the combustion chamber and burnt (although too much breathing here will reduce performance, induce pinking etc so it's still a bad thing). When you've an open cone filter, it will just drip/flow to the lowest point on your intake system - often the lower edge of a cone filter.
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