Which of the following is true about spark plugs?

Spark plugs are essential components of internal combustion engines, and they indeed come in various types and sizes. Different engines require spark plugs that are specific to their design, including variations in heat range, electrode material, and thread size. Each engine manufacturer typically specifies the appropriate spark plug for their engine models based on these parameters. This diversity allows for optimized engine performance, efficiency, and reliability based on the specific ignition and combustion requirements of the engine.

In contrast, the other statements lack accuracy. Spark plugs cannot maintain their effectiveness indefinitely; they require periodic replacement due to wear and the buildup of carbon deposits. They also significantly influence engine performance, as the right spark plug can enhance combustion efficiency and improve overall engine functionality. Furthermore, it’s not correct to assert that spark plugs are only manufactured in one size, as this would ignore the extensive range produced to accommodate a multitude of engine specifications.