How Many Car Spark Plugs Should Be Replaced at Once?
2 Answers
Spark plugs should be replaced all at once. The discharge gap between new and old spark plugs differs, as does their resistance. Not replacing all of them may lead to issues like engine shaking, difficulty accelerating, and increased fuel consumption. Spark plugs have a certain lifespan, and products from the same batch should have similar quality and longevity. If one or two spark plugs show problems, it indicates that the others are nearing the end of their lifespan as well. Spark plugs, commonly known as sparkers, function by discharging the high-voltage pulse electricity sent through the high-tension leads, breaking down the air between the two electrodes to generate a spark, thereby igniting the air-fuel mixture in the cylinder. The main types of spark plugs include standard spark plugs, projected insulator spark plugs, electrode spark plugs, seat spark plugs, pole spark plugs, and surface gap spark plugs.
Spark plugs are best replaced all at once. Why? I've been driving for ten years and have learned this the hard way. Last time, trying to save money, I only replaced the one that was faulty, and the next day the engine started shaking nonstop with poor ignition. After inspection, the mechanic explained that spark plugs need to work in sync—mismatched old and new ones can cause ignition delays and fuel waste. Modern cars have as many spark plugs as cylinders; for example, a four-cylinder engine has four. Lifespan depends on material: nickel alloy lasts around 30,000 km, while platinum or iridium can endure up to 100,000 km, but never mix them. Labor costs for removal and installation are high, and replacing only some often leads to recurring issues. It’s better to replace them all during routine maintenance—it’s not expensive and saves hassle in the long run. Also, don’t forget to regularly inspect the entire ignition system, including coils, to ensure safe driving.
