Spark Plug Change: When, Why & How

If your engine feels a bit lazy, the check‑engine light is on, or fuel consumption has gone up, the spark plugs are probably the first thing to look at. They’re cheap, they last a while, and swapping them yourself can save you a visit to the garage.

Why Change Spark Plugs?

Fresh plugs give a clean, strong spark. That means smoother idling, better acceleration, and lower fuel use. Over time the electrodes wear down, carbon builds up, and the gap widens. When the gap gets too big the spark can’t jump, so the engine misfires or runs rough. Replacing them restores the original compression and keeps the combustion process efficient.

Most manufacturers recommend a change every 30‑60 000 km, but it really depends on the plug type. Copper plugs wear fastest, while iridium or platinum can stretch to 100 000 km. If you drive hard, tow heavy loads, or run a performance engine, stick to the shorter interval.

Step‑by‑Step Spark Plug Replacement

Here’s a straight‑forward way to get the job done in under an hour:

1. Gather tools. You’ll need a spark‑plug socket (usually 5/8" or 13/16"), a ratchet, an extension bar, a torque wrench, and a spark‑plug gap gauge.
2. Cool the engine. Let the car sit for at least 15 minutes after running. Hot plugs can break easily.
3. Locate the plugs. Remove the ignition cover if there is one. Follow the coil or plug‑wire to each plug.
4. Remove the old plug. Loosen the socket counter‑clockwise and pull the plug out gently. Watch for any debris that might fall into the cylinder.
5. Check the gap. Even new plugs need the correct gap for your engine. Use the gauge and adjust the gap by gently bending the ground electrode if needed.
6. Install the new plug. Hand‑tighten the plug first, then use the torque wrench to reach the spec (usually 20‑30 Nm). Over‑tightening can crack the cylinder head.
7. Reconnect the coil or wire. Make sure it snaps into place securely.

Repeat the process for each cylinder. When you’re done, start the engine. It should run smoother, and any misfire codes should disappear.

Quick tips: keep a small container for the old plugs so you don’t lose them, and wipe the spark‑plug holes with a clean rag before inserting the new plugs. If you notice oil or coolant on the old plugs, that could signal a deeper issue and you should get a professional look.

Changing spark plugs yourself isn’t rocket science, but it does need a bit of care. Doing it regularly keeps your engine humming, saves fuel, and avoids costly repairs down the road. So next time you see a misfire warning, grab the socket set and give those plugs a fresh start.