I know the general ideas about picking up on whats going on iside your engine by looking at the plugs, but I can never seem to remember which is which. I changed my plugs last week and the plug electrodes(?) were mostly light ash grey with very small patches of light brown, but what really worried me was the thick, crusty, sooty residue around the collar(?) at the bottom of the plug. Any body give me an idea of what's going on?
