How long will a spark plug last?

A Even when a spark plug is correctly used, periodic replacement is required as it is a consumable item.

Examples of problems caused by excessively long periods of use: Worn-out electrodes will have difficulty in sparking.
Deposits accumulated on the firing end may induce abnormal combustion, causing problems that include melting of the electrodes or damaging engine.

These spark plugs require replacement.

It must be noted that these phenomena may also be caused by inadequate engine servicing (fuel systems and ignition system) and incorrect spark plug selection.