How spark plugs work, the differences between types, and the replacement intervals that keep your engine running right.
Spark plugs ignite the fuel-air mixture in your engine’s cylinders. They’re small, but when they wear out, your engine’s performance, fuel economy, and emissions all suffer.
1. How Spark Plugs Work
Each spark plug creates a small electrical arc that ignites the compressed fuel-air mixture in the cylinder. This happens thousands of times per minute. Over time, the electrode wears down and the gap widens, making the spark weaker and less consistent.
2. Types of Spark Plugs
Copper/Nickel plugs are the most affordable but wear out fastest — expect to replace them every 25,000 to 30,000 km. Platinum plugs last longer (40,000 to 50,000 km) and provide more consistent performance. Iridium plugs are the most durable, lasting 60,000 to 75,000 km, and offer the most precise spark. Your engine is designed for a specific type — always match what the manufacturer recommends.
3. Signs Your Spark Plugs Need Replacing
Rough idling, hesitation during acceleration, poor fuel economy, difficulty starting, and engine misfires are all common symptoms. If your check engine light is on, worn spark plugs are one of the first things to check.
4. Why Timing Matters
Waiting too long to replace spark plugs doesn’t just hurt performance — worn plugs can damage the ignition coils, which are significantly more expensive to replace. Staying on schedule with spark plug replacement protects the rest of your ignition system.