Here's what could be causing it:
* Worn Piston Rings: This is the most common cause. Worn piston rings allow combustion pressure and oil to leak past the pistons into the crankcase and then, via the PCV system (Positive Crankcase Ventilation), into the intake.
* Worn Valve Guides/Stem Seals: Worn valve guides or stem seals can allow oil to leak past the valves into the combustion chamber.
* PCV System Problems: A malfunctioning PCV valve or clogged PCV system can cause excessive crankcase pressure, forcing oil into the intake.
* Excessive Crankcase Pressure: A number of things can cause this, including a blocked crankcase breather, a failed PCV valve, or a problem with the engine's ventilation system.
* Crankcase Ventilation System (CCV) Issues: This system is responsible for removing blow-by gasses from the crankcase. Problems within it can lead to oil being forced into the air intake.
* Damaged or leaking engine components: Less likely, but possible, a major engine leak elsewhere could indirectly contribute to oil in the air filter.
What to do:
1. Don't drive the vehicle: Continuing to drive could cause serious engine damage.
2. Check the oil level: Is the oil level low? This reinforces the suspicion of oil leaks.
3. Inspect the PCV valve: Is it clogged or sticking? Replace it if necessary.
4. Consult a mechanic: This is crucial. Diagnosing the exact cause requires a professional inspection. Ignoring this problem will likely lead to further damage, potentially requiring a costly engine rebuild or replacement.
Oil in the air filter is a significant warning sign of internal engine problems. Ignoring it will almost certainly result in worse problems and more expensive repairs down the line.
