With the Kia spark plug in place and functioning, a controlled explosion can take place in your engine. This is a very active component of the ignition system that must be working correctly for your engine to operate most efficiently. There is a specific spark plug for each Kia engine that is manufactured today, although some can be interchanged. The variables of the spark plugs include the depth in which if goes into the combustion chamber, the heat range of the arc it produces, and the gap at which the electrode is set at. Each of these variables must be correct for all of the plugs installed on your engine. There is a Kia spark plug for each cylinder in your engine. All of them must be the same so a smooth running engine can be achieved. Once in place a spark plug generally does not just fail. The most common reason for the plug to misfire is that it is just worn out. The electrode at the end of each plug is the section of this ignition component that will show signs of wear and the reason it will have to be replaced. This procedure is called a tune up. It can also become fouled out if an excess of oil, fuel or water enters the combustion chamber; but this is rare and means you have another problem on your Kia. A tune up should not only be the replacing of the spark plugs but also the air and fuel filters along with inspection of the ignition wires running to the plugs. This will make it possible for you Kia engine to achieve the best possible fuel mileage and performance when on the road.