Maintenance of spark plugs

From old spark plugs which have been removed from the engine, you can clearly recognise from the damage patterns whether the engine is working well or not. A spark plug that was removed from a well-functioning engine appears "dried out" - the areas around the electrodes appear dry, grizzled and exhibit tones ranging from white to yellow to brown. The electrodes, as well as the visible lug of the insulator do not normally show any significant signs of damage.