How to Determine When to Replace Car Spark Plugs?

[DylanAnn]

Signs that spark plugs need replacement primarily include noticeably high fuel consumption and sluggish vehicle performance with unresponsive throttle. 1. Difficult ignition. Whether during cold or warm starts, achieving instant ignition becomes nearly impossible—even successful starts take 5-6 seconds. This occurs because the spark plug electrodes are severely worn, with rounded edges around the center electrode resulting in weak, unstable spark discharge. Additionally, excessive spark plug gap reduces spark intensity and penetration power, making it difficult to ignite the air-fuel mixture. 2. Increased fuel consumption. Normal consumption of 7-8L/100km may suddenly rise to over 10L. The exhaust emits unburned fuel droplets (sounding like falling metal beads), requiring more frequent refueling. 3. Noticeable power loss during hill climbs or sudden acceleration. Especially when carrying passengers, full throttle fails to deliver expected power. This happens because degraded spark plug performance increases misfire rates, causing incomplete combustion of the air-fuel mixture before exhaust. The engine cannot achieve its designed maximum power output, resulting in throttle lag. Spark plug replacement intervals: Under normal maintenance conditions, replacement is recommended at 40,000-60,000 km. However, this varies by brand and engine type—always consult your owner's manual. General replacement guidelines: • Platinum spark plugs: 40,000 km • Standard nickel alloy spark plugs: 20,000 km • Iridium spark plugs: 60,000-80,000 km