Starting in the mid-1990s, iridium-tipped plugs appeared. Iridium is even harder than platinum, so these plugs were intended to last longer. They are also claimed to slightly increase combustion ...

Ordinary plugs need replacing every 30,000 miles, but platinum and iridium spark plugs could last up to 55,000 miles. If your vehicle has symptoms like hard starting and poor idling, it could mean ...