Final answer:
The recommended torque value for tightening a spark plug is usually specified by the vehicle's manufacturer, but typically ranges from 10 N·m to 20 N·m. Without specific engine or spark plug details, an average safe value to use would be 15 N·m. Always use a torque wrench to achieve the precise value for optimal engine performance and plug longevity. Option C is the correct answer.
Step-by-step explanation:
Recommended Torque for Tightening a Spark Plug
When tightening a spark plug, it is crucial to apply the correct torque to ensure that the spark plug is properly seated and sealed within the engine, without being over-tightened which could damage the plug or engine. The recommended torque value depends on several factors including the spark plug size, thread pitch, and the engine's specifications. Manufacturers provide torque specifications for spark plugs, and it is always best to consult the vehicle's manual or the spark plug manufacturer's recommendations for the exact value.
However, without specific details for the type of engine or spark plug, a general guideline torque value for common spark plugs is often between 10 N·m to 20 N·m. Torque values lower than 10 N·m might not be sufficient to ensure a good seal, while values much higher than 20 N·m could strip the threads or break the spark plug. Hence, among the provided options, 15 N·m (c) is a safe average torque value for many spark plugs if no specific recommendation is given.
It is important to use a torque wrench when tightening a spark plug to reach the precise torque value. Applying the correct torque ensures that the spark plug has a good electrical connection and is properly sealed within the combustion chamber, which is critical for engine performance and longevity.
The correct answer from the provided options is: 15 N·m (c).