Spark plugs - is it trying to tell me something?

[AresROC]

While doing the cylinder compression test (Thread), I pulled out the spark plugs, and found 1 of them to be different than the others:


Spark plugs, cylinders 1~4 from left to right.

Those are NGK Platinum plugs, two days old. All plugs still have a pristine white ceramic tip, except for cylinder 1's. What is it trying to tell me? Am I burning oil or running rich on cylinder 1? Only one side of plug 1 is stained, facing the camera. The other 3 sides are clean... Please help!

[96paseo]

Thats only some minor discoloration. Nothing to worry about. The ceramic insulator on all the plugs will look like that as they wear. Running rich would show up as a wet plug or a black carbon coating. Burning oil usually shows up as white ash that will flake of the ground electrode.