Why Do I Need to Change My Spark Plugs?

Most spark plugs are designed to last more than 100,000 miles, though some vehicle manufacturers recommend they be changed every 60,000 miles or sooner. Precise fuel management and spark timing, plus the use of precious metals such as platinum and iridium in the plugs, often enable spark plugs to last more than 10 years without significant degradation in performance. They should be changed sooner only if they’re fouled by gas or oil, cause the engine to misfire, or are diagnosed as the cause of hard starting, poor acceleration or low fuel economy.