Is the electrode part of the plug covered in oil or the outside? From your original post it would seem that the oil is on the outside. If that is the case then the o-ring that seals the plug well off from the head probably went bad. It s a cheap part to replace but you will have to pull the valve covers to do ti.

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"It's not about how fast you can go, but how well you can go fast."

Bob in Richmond

'97 S320 (LWB), Ruby Red Metallic, 73k miles
'97 S420V, Smoke Silver Metallic, 155k miles