How to Make Your Car Last Forever: Avoid Expensive Repairs, Improve Fuel Economy, Understand Your Warranty, Save Money

Here we have two sparkplugs. One is brand new, and the other has a heavy carbon deposit buildup. This is
typical of sparkplugs in use for more than 20,000 miles. The reason for the carbon buildup is inefficient
combustion from a weak spark. The spark gets weak from worn sparkplug wires, ignition components, and
dousing of the spark with too rich and wet a fuel mixture. All these things figure into sparkplug life, hence the
reason for removing, inspecting, and cleaning or replacing them every 25,000 miles. Leave them in too long
and you have a recipe for drivability problems, poor fuel mileage, and increased tailpipe emissions.