Replace Spark PlugsMike Bumbeck8/10/07 1:00pmFiled to: And You Will Know Us by the Trail of PartsFeaturespark plugcar caredrivewayfixing your carHow ToTools29EditPromoteShare to KinjaToggle Conversation toolsGo to permalinkAlong with swapping out the air filter and changing the oil, replacing the spark plugs is one of the few things left that require service on a modern gasoline engine. Some newer than the twenty-year old junk classics in our garage have negated even this task with spark plugs made of space-age materials that can live with their head stuck in a combustion chamber for 100K miles or more. The first and most obvious task of the spark plug is to light the gasoline and air mixture aflame when the piston reaches the top of its compression stroke. The resulting burn pushes the piston back down in the cylinder. So it goes. The second and less obvious function of a spark plug is equally important.