How to Determine When to Replace a Car's Spark Plugs?

[Jess]

Methods for determining if spark plugs need replacement: Remove the spark plugs for observation and assess their condition based on the following visual color indicators. Normal spark plugs will have insulator skirts and electrodes appearing gray-white, gray-yellow, or light brown. Properly functioning spark plugs exhibit a reddish-brown insulator skirt with an electrode gap between 0.8-0.9mm and no signs of electrode burning. If the spark plugs are soiled with oil or deposits but remain undamaged, they can continue to be used after cleaning off the oil and deposits. If the spark plugs are severely damaged, showing signs such as blistering at the tip, black streaks, cracking, or melted electrodes, the cause of the damage should be identified. After troubleshooting, replace the spark plugs with new ones. Additionally, if the spark plugs appear blackened as if smoked, it indicates incorrect heat range selection or a rich fuel mixture, possibly with oil leakage. Damaged spark plugs can directly cause various issues such as electrical leakage in the vehicle's ignition system, increased fuel consumption, reduced power, and most notably, difficulty in ignition, affecting the vehicle's normal operation. Severe spark plug erosion, including blistering, damage, or melted and eroded electrodes, clearly indicates that the spark plugs are ruined and should be replaced.

[OHope]

I have a five-year-old car that's been feeling sluggish during acceleration lately, especially when going uphill, and the fuel consumption has also increased compared to before. During the last maintenance check, the mechanic said the spark plugs needed replacement based on the mileage—they typically need inspection every 30,000 to 60,000 kilometers. He showed me the removed spark plugs, and the electrodes were eroded and blackened. Actually, if you notice the engine taking longer to start or the steering wheel vibrating noticeably at idle, it's most likely a spark plug issue. I remember one winter morning when it took three attempts to start the car, but after replacing the spark plugs, it ran smoothly right away. You can usually check for oil stains around the ignition coils yourself, but it's best to use professional tools to test the ignition waveform. Definitely don't push it until it completely fails on the road.

[MacRonan]

I just changed my spark plugs last week, and the most noticeable difference is how the engine sounds now. Before, when waiting at a red light, I always felt the car slightly trembling, like a phone vibrating, and I could hear the engine making a 'puttering' noise when accelerating. The mechanic gave me a few practical tips to check: pay attention to the first ignition time when starting a cold engine - if it takes more than three seconds, be cautious; when driving on the highway, press the accelerator hard to see the acceleration response - if it feels sluggish even when the pedal is floored; the most direct method is to remove the spark plugs and check their condition - they should normally be tan in color, but if they're severely blackened with carbon deposits or the electrodes are rounded from burning, they must be replaced. Regular inspections are crucial, especially for older cars - don't wait until you're stranded on the road to start worrying.

[DelReese]

Over the years in auto repair, I've noticed most car owners overlook spark plug lifespan. Actually, four indicators are most accurate: the check engine light stays on with misfire codes; noticeable fuel consumption increase of 1-2L/100km; stronger exhaust smell with unburned gasoline odor; and severe jerking during acceleration like being pulled back. New spark plugs have clean white ceramic parts that turn yellow and cracked when worn. I've encountered owners who didn't change them for 100,000 km, resulting in burnt ignition coils - replacing the entire ignition system costs three times more than spark plugs. Recommended replacement intervals: OEM nickel alloy at 30-40k km, platinum at 60k km, and iridium can last up to 100k km.