Do Spark Plugs Affect Fuel Consumption?
2 Answers
Spark plugs do affect fuel consumption. If a spark plug is damaged, it can directly lead to increased fuel consumption in a car. Methods to determine if a spark plug is damaged: Remove the spark plug and observe it. The condition of the spark plug can be judged based on the following appearance colors. A normal spark plug has an insulator skirt and electrodes that appear gray-white, gray-yellow, or light brown. A properly functioning spark plug has a reddish-brown insulator skirt, with an electrode gap between 0.8-0.9mm and no signs of electrode burn. If the spark plug is contaminated with oil or deposits but is not damaged, it can continue to be used after cleaning off the oil and deposits. If the spark plug is severely damaged, with signs such as blistering at the top, black streaks, cracks, or melted electrodes, the cause of the damage should be identified. After troubleshooting, replace the spark plug with a new one. Additionally, if the spark plug appears black as if smoked, it indicates that the wrong heat range was selected or that the air-fuel mixture is too rich, with oil creeping up. Steps to replace a spark plug: Open the hood and lift the plastic cover of the engine. Remove the high-voltage wires, marking each cylinder's position to avoid confusion. Use a spark plug socket to remove the spark plugs one by one. While removing them, check for external debris like leaves or dust and ensure everything is cleaned thoroughly. Place the new spark plug into the spark plug hole, hand-tighten it a few turns, and then use the socket to tighten it further. Reinstall the high-voltage wires according to the firing order, and then secure the cover.
Spark plugs indeed affect fuel consumption. Based on my experience tinkering with cars, when they fail, it leads to ignition misfires, forcing the engine to inject more fuel to compensate for combustion, directly causing fuel consumption to surge by over 10%. I remember last time my car had unstable idling and weak acceleration—it turned out the spark plug electrodes were carbon-fouled, reducing ignition efficiency and increasing fuel consumption by 15%. After promptly replacing them, everything returned to normal. Spark plugs should be inspected or replaced every 40,000–60,000 km, especially in older cars, which are more sensitive. Cleaning them also helps, but don’t delay too much—once problems arise, it wastes fuel and harms the engine. Developing regular maintenance habits saves fuel and hassle while preventing major repair costs.
