What are iridium spark plugs?

Created by Jonathan Fry, Modified on Tue, 1 Apr at 9:53 PM by Jonathan Fry

Iridium spark plugs are a type of spark plug used in internal combustion engines, known for their durability and performance. They have a small electrode tip made of iridium, a rare and precious metal that’s part of the platinum group. The key features that set them apart are their high melting point (around 2,450°C or 4,442°F), extreme hardness, and resistance to corrosion and wear. This makes them ideal for generating the spark needed to ignite the air-fuel mixture in an engine.

They’re expensive for a few reasons. First, iridium itself is scarce—rarer than gold or platinum—and it’s typically mined as a byproduct of other metals like nickel or copper, which limits supply. Second, the manufacturing process is more complex due to iridium’s properties; it’s tough to work with because of its hardness and high melting point, requiring precision to form the tiny electrode tip (often just 0.4 to 0.6 mm in diameter). Third, these plugs last a lot longer—up to 100,000 miles or more compared to 20,000-40,000 for traditional copper plugs—so you’re paying for longevity and efficiency. They also improve engine performance, like better fuel economy and smoother operation, especially in modern high-compression or turbocharged engines.

The cost reflects the material rarity, production difficulty, and the premium performance they offer. A single iridium spark plug can run anywhere from £10 to £20 or more, while copper ones might be £5 or less.