spark plug covered in oil

[xilef]

A couple of weeks ago I've noticed vibrations while driving my '92 Maxima. I checked the spark plugs and one of them was covered with oil on the inside. The compression ratios checked out fine. I've changed the spark plug but it keeps on vibrating. I assume it's vibrating because the oil puts out the spark generated by the plug so one piston ends up not firing. I would really appreciate if someone can tell me the possible causes for the leak and maybe the price range of the fix.

[navysnail]

maby a valve guide or an oil ring. none of those would cause bad compression. other than that, i dont really have any other ideas, maby someone else will have another source for the oil. are you loosing oil fairly quickly?