CC: Factory-recommended spark plug replacement intervals have consistently been in the 100,000-120,000-mile range for the past two decades thanks to the efficiency of precious-metal spark plugs, these spark plugs can still continue performing well long after these intervals have been reached. However, it is important to keep an eye on spark plug performance as they approach 100,000 miles of use. As electrodes wear over time, spark plugs require more voltage to fire. If this wear goes undetected, this strain can cause misfires and firing voltages can increase. This can cause the coils to fail prematurely.

But, more manufacturers that are utilizing small displacement engines that have direct injection, turbocharging and variable valve timing are actually rolling back spark plug replacement intervals to 35,000 to 40,000 miles, due to hotter temperatures and higher combustion pressures. These are not copper core spark plugs, there are platinum and iridium fine wire spark plugs. This is why it is critical to look up the maintenance schedule for the vehicle. The most important thing to remember when you are ordering spark plugs is to never downgrade. If a car came with a fine-wire platinum spark plug, the replacement plug needs to match the original specifications, even if the vehicle has 300,000 miles.

This video is sponsored by Autolite.