How Many Spark Plugs Should Be Replaced Each Time?

[LaNaomi]

Four spark plugs need to be replaced at a time in a car. Theoretically, even if you replace one spark plug with the same brand and model, the discharge gap and resistance value between the new and old spark plugs will differ. Not replacing all of them may result in issues such as engine shaking, difficulty in acceleration, and increased fuel consumption. Steps for replacing spark plugs: Open the engine hood, lift the plastic cover of the engine, remove the high-voltage distributor wires, and mark 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 any external debris like leaves or dust and ensure they are thoroughly cleaned. 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 removed high-voltage distributor wires according to the firing order, then secure the cover. If a spark plug is damaged, it can directly cause issues such as leakage in the vehicle's ignition system, increased fuel consumption, and reduced power. The most critical issue is difficulty in ignition, affecting the vehicle's normal operation. Severe spark plug erosion, such as scarring at the top, electrode melting, or burning, indicates that the spark plug is damaged and should be replaced.

[AliviaLee]

I remember last month when I helped my neighbor fix his old four-cylinder car, there was an issue with the spark plugs. I told him they should always be replaced in full because it's a four-cylinder engine, so all four spark plugs need to be changed. If you only replace one or two, the uneven wear between the old and new spark plugs can cause inconsistent ignition timing in the engine. At best, this leads to increased fuel consumption and severe engine shaking; at worst, it could burn out the ignition coil and drag down overall performance. I usually drive a manual transmission car, and during regular maintenance, I also insist on replacing all spark plugs. I check them every 30,000 kilometers or two years, and replacing the spark plugs proactively can prevent major issues. When buying a car, always ask about the number of cylinders—don’t cut corners and risk safety hazards. Safety comes first.

[DeTucker]

I've always enjoyed DIY car repairs, and the number of spark plugs really depends on how many cylinders your engine has—replace four for a four-cylinder, six for a six-cylinder. Replacing them all at once is the most hassle-free approach. Last year, I tried replacing only some, and the engine kept misfiring during startup, making the car unstable. Spark plugs ignite the gasoline, and if you don't replace them all, the older, faster-degrading plugs can interfere with the new ones, leading to incomplete combustion. I recommend checking your manual beforehand to confirm the cylinder count, buying the right model, and having heat-resistant tape and a wrench ready. Doing it yourself takes less than an hour—safe, cost-effective, and saves you the hassle of returning to the shop.

[Hillary]

Having driven for thirty years and changed spark plugs over a dozen times, experience has taught me to replace the entire set at once. My six-cylinder van gets all six new spark plugs every 50,000 kilometers on schedule—a full replacement prevents misfires or carbon buildup caused by inconsistent spark intensity. Replacing only individual spark plugs is a shortsighted approach that can lead to uneven engine output and accelerated wear. Remember to prepare tools and materials according to your vehicle’s cylinder count—don’t cut corners to ensure long-term smooth driving.