If your car runs on gasoline, it has spark plugs. (For diesel and electric vehicles, spark plugs aren’t used.) The way an engine runs is by delivering a spark to compressed fuel and air. This happens within four, six, or eight different cylinders, one spark plug for each cylinder. The spark plug receives voltage from the ignition system, allowing them to fire when the cylinder has maximum compression of air and fuel in it. The spark plug ignites the air in the cylinder, and the engine creates forward motion as a result of that explosion   6 Signs of Spark Plug Failure Spark plugs fire thousands of times a minute. Normally, they operate perfectly, allowing your engine to run smoothly. But eventually, after about 50,000 to 100,000 miles on average, you’ll encounter sp ... read more