Here's why:
* Valve Stem Seals: These small seals prevent oil from seeping past the valve stems into the combustion chamber. When they wear out, oil can leak down the valve stem and collect on the spark plug, dripping out. Since it's happening on *several* plugs, it's unlikely to be just one bad seal.
* Other less likely, but possible causes: While less probable given multiple plugs are affected, consider:
* Worn piston rings: This would lead to oil burning and potentially oil in the cylinders, but usually wouldn't drip *directly* onto the spark plugs like worn valve stem seals. You'd see more smoke from the exhaust.
* A cracked valve cover: This would allow oil to leak into the engine's upper parts, but again, wouldn't necessarily drip *specifically* onto the spark plugs. You'd see oil elsewhere in the engine bay.
* A severely damaged PCV valve: A very clogged or broken PCV valve could lead to excessive crankcase pressure, forcing oil past seals, but the widespread nature across multiple plugs again points more towards valve stem seals.
Why multiple plugs? Worn valve stem seals are more likely to affect multiple cylinders over time due to the consistent wear and tear on all valves.
What to do: This is not a DIY fix unless you have extensive engine repair experience. The valve stem seals require a significant amount of disassembly to replace, and it's best handled by a qualified mechanic. Ignoring the problem will lead to further engine damage, including misfires, poor combustion, and ultimately engine failure.
