You'll never find a spark plug as big and beautiful as the one pictured; however, the tiny little parts play a pretty huge role in making cars do what they do. Failure to replace them can be detrimental to your car's engine.
The spark plug's job is to send an electric spark through the engine's combustion chamber to produce power. It is commonly suggested that drivers should have their spark plugs changed every 30,000 or 100,000 miles, depending on the type of spark plug used. If you rarely pay attention to your odometer (I'm guilty), you should be aware of the telltale signs that your spark plugs need to be replaced.
-If your car is not starting correctly, it is not always fair to place the blame on your battery. Your spark plugs ignite a mix of fuel and air to produce power. If they are not performing properly, they will not produce enough power to start your engine. Bad spark plugs can also cause your battery to drain.
-When sitting at a stop light with an idle engine, how does your car feel? Like an airplane in turbulence? Like a tractor plowing a field? While your engine is resting, your car should sit still and quiet.
-Gas is expensive. It never goes on sale. I've never seen clearance gas, buy one gallon-get one free gas, gas bundles...it's just expensive. A decrease in your car's gas mileage is a noticeable annoyance that could be due to worn spark plugs.
-If your car's every move can be traced by a cloud of smoke, get those spark plugs changed. Worn plugs can lead to higher emissions.