Related: Do Diesel Engines Have Spark Plugs? The typical automotive spark plug is about the size of ... Starting in the mid-1990s, iridium-tipped plugs appeared. Iridium is even harder than ...

It promotes the benefits of copper spark plugs over iridium ones. Although Accel has a 4.5-star rating on Amazon, one reviewer pointed out that these copper plugs only last about half as long as ...