There is a (small) spring-loaded reciprocating mechanical element - aka a moving part - in many (all?) spark plugs [0]. Lubricating this reciprocating interface

There is a (small) spring-loaded reciprocating mechanical element - aka a moving part - in many (all?) spark plugs [0]. Lubricating this reciprocating interface is an active research area. [0] http://4.bp.blogspot.com/--EcUF2vWkUM/T7aL828jmdI/AAAAAAAACPg/BVrIW3eRdI4/s1600/spark_plug.png http://4.bp.blogspot.com/--EcUF2vWkUM/T7aL828jmdI/AAAAAAAACP...