What are the reasons for replacing spark plugs?

[LaJayce]

The reasons for replacing spark plugs are: 1. Different spark plugs have a certain mileage limit, and they need to be replaced if the specified mileage is exceeded; 2. If abnormal phenomena occur in the spark plugs, such as electrode erosion, excessive carbon deposits, cracked insulators, or excessive gap, the spark plugs need to be replaced. The condition of the spark plugs affects the engine's power output—simply put, it affects driving performance. The driver may experience symptoms like lack of power; 3. When the engine malfunctions, such as shaking, poor acceleration, or difficulty starting, the spark plugs should be checked first. If the engine issues are caused by faulty spark plugs, they also need to be replaced.

[Jean]

Last time I went to replace the spark plugs precisely because of inexplicably increased fuel consumption. After driving 60,000 kilometers, I clearly felt the car struggling during startup and sluggish acceleration. When the mechanic showed me the old spark plugs, the electrodes were nearly worn flat with excessively large gaps. In such condition, the ignition energy weakens, leading to incomplete combustion of the air-fuel mixture, forcing the engine to compensate by injecting more fuel. Continuing to drive like this would not only waste fuel but also damage the engine, and the catalytic converter could easily fail. That's why regular spark plug replacement is crucial. For my Japanese car model, the maintenance manual specifies replacement every 50,000 kilometers. I'm even planning to upgrade to iridium spark plugs to extend the replacement interval.

[Brandon]

As someone who frequently drives long distances, I place great importance on the condition of the ignition system. Spark plugs can develop various issues after prolonged use, with carbon buildup on the electrodes being the most common. Once on the highway, I felt the engine shaking and noticed unstable idling. Upon inspection, I found the ceramic body of the spark plug had turned yellow. This condition can easily lead to overheating and damage of the ignition coil, resulting in more expensive repairs. In fact, preventive replacement is the most cost-effective solution. Standard nickel-alloy spark plugs should be replaced around 40,000 kilometers, while double-platinum ones can last up to 80,000 kilometers. I remember after the last replacement, the throttle felt noticeably lighter, and the power response became much sharper.

[MacBenjamin]

The harm of not replacing spark plugs on time is greater than imagined. When the electrode gap becomes larger, a higher voltage is required to generate a spark, which accelerates the aging of the ignition coil. Spark plugs with severe carbon deposits can also cause cylinder misfires, resulting in uneven engine operation. Especially for turbocharged models, stable ignition is even more crucial due to the high cylinder pressure. I usually judge based on three criteria: difficulty in cold starts, engine shaking during acceleration, and a sudden increase in fuel consumption. If any of these symptoms appear, it's time to check the spark plugs. Nowadays, iridium-platinum spark plugs have a long lifespan but are also more expensive.

[StAngelo]

I used to think spark plugs could last a long time, but a mechanic later taught me to check their condition. Normal spark plug electrodes should be grayish-white, but mine had turned black with oil stains. This is a sign of an overly rich fuel mixture, and the ignition timing is also off. Prolonged operation in this condition can leave unburned gasoline in the cylinders, diluting the engine oil and damaging the engine. Now I proactively replace them every 3 years, and it's crucial to choose the heat range model recommended in the vehicle manual—incorrect heat range can lead to overheating and melting. The most noticeable change after installing new spark plugs is the reduced exhaust odor, and passing emissions tests has become much easier.

[StEmma]

A failed spark plug is like the 'heart disease' of an engine. I personally experienced the embarrassment of stalling at idle. The old spark plug I removed had its center electrode eroded into a V-shape, and the ceramic body had cracks. This causes the ignition position to shift, directly reducing combustion efficiency. Even worse, if the electrode melts and falls into the cylinder, it could lead to a major overhaul. Now, I determine the replacement cycle based on the material: nickel alloy at 30,000 km, platinum at 60,000 km, and iridium at around 80,000 km. Also, it's important to choose the correct thread length—using the wrong model can cause it to hit the piston.