Iridium vs Copper Spark Plugs: Which Is Better for Your Car?

When it comes to spark plugs, iridium, a rare, ultra-durable metal used in high-performance spark plug electrodes and copper, a traditional, highly conductive metal commonly found in standard spark plugs are the two main choices most drivers face. Iridium plugs are known for their long life and consistent spark, while copper plugs deliver strong ignition but wear out faster. The right pick depends on your car’s engine, how you drive, and what you’re willing to spend. Many modern cars come with iridium plugs from the factory—not because they’re fancy, but because they last longer and keep engines running smoothly under pressure.

Here’s the simple truth: iridium lasts up to three times longer than copper. A good iridium plug can go 80,000 to 100,000 miles before needing replacement, while copper often needs changing by 20,000 to 30,000 miles. That’s not just a convenience—it’s a cost saver over time. But copper has its strengths. It conducts heat and electricity better than iridium, which means it can deliver a stronger spark under high-load conditions, like towing or aggressive driving. For older cars with basic ignition systems, copper might even feel more responsive. But if your engine is tuned, modern, or fuel-injected, iridium’s precision and stability make it the smarter move. You’ll notice fewer misfires, better fuel economy, and smoother idling.

It’s not just about the metal, though. What matters most is matching the plug to your engine’s design. Some engines need the fine-tip electrode of an iridium plug to ignite lean fuel mixtures efficiently. Others work fine with copper’s wider electrode because they’re designed for simpler combustion. Mixing them up can cause problems—even if the plug fits physically. Always check your owner’s manual or use your VIN to confirm the right type. Don’t assume more expensive means better. If your car came with copper, swapping to iridium won’t magically boost horsepower. But if you’re replacing worn plugs and want to cut down on future maintenance, iridium is the way to go. And if you’re on a tight budget and drive gently? Copper still does the job—just be ready to replace it sooner.

Below, you’ll find real-world advice from drivers and mechanics who’ve tested both types under UK conditions. From diagnosing misfires to understanding why your car runs rough after a plug change, the posts here cover exactly what you need to know—no fluff, no hype, just clear facts based on what actually works on the road.