The spark plug is a key component in the ignition process of any combustible engine. The working principle of a spark plug is common for all combustible engines. During every ignition process, a spark plug is subject to a lot of carbon deposition at the engine heads where actual fuel burning process starts.
With the high deposits and dirt on the spark plug, the spark plug tends to pull in higher voltage to create a spark or sometimes the ignition would never happen. Hence manufacturers have given a km limit when customers need to check and change their spark plugs. The spark plug is the easiest and the simplest component to replace in a vehicle.