What does the spark plug face say?

Spark plugs are, to some extent, the main witnesses to the combustion process. The appearance of the spark plug electrodes (spark plug face) tells the specialist whether the engine is operating optimally. Therefore, when checking dismantled spark plugs, pay attention to the following points.

Top of the insulator from light gray to gray: the preparation of the air-fuel mixture is well adjusted - the engine runs economically.

Whitish insulator top: too lean fuel-air mixture - check the CO content; the ignition timing may have been incorrectly set; control unit defective.

Soot-like black deposits: spark plug does not reach self-cleaning temperature (frequent movement only for short distances), incorrect heating value, air-fuel mixture too rich, CO content too high, lambda probe defective.

Oil layer on the electrodes: defective piston rings, valve guides or valve stem gaskets. It is also possible that you have used motor oil or fuel with additives. Replace the spark plugs, change the oil and brand of gasoline, and recheck the condition of the spark plugs.