The Mazda spark plug wires are the conduit that provides the pathway for the electrical charge to go from the ignition coil or distributor to the spark plug. The current form of these ignition components makes use of glass or carbon fibers for the transfer of the electrical charge which is covered with a protective polymer coating. In the past the use of copper wire was used instead of the fibers. There is an individual spark plug wire for each of the cylinders on your Mazda engine. Some smaller engines may have a coil-on-plug configuration; using only one wire to jump from one cylinder to another. For the engine to run smoothly, each one must be able to transmit the same electrical voltage. If one of them is damaged for any reason, the engine will no longer be able to perform as it should. The reason for the switch to carbon composite fibers from copper cores in the Mazda spark plug wires is the increased level of efficiency these fibers can transmit the impulse. It is all about a reduction in resistance the electrical impulse experiences in its travel down the wire. As spark plug wires age, the resistance they have in their ability to transfer this electrical charge increases. They become brittle in time due to heat related stress they endure under the hood of the Mazda. As the number of fibers that have cracks in them or break increases, the resistance rises reducing their efficiency in the transfer of the electrical impulse. This is the leading reason why Mazda owners have to replace their spark plug wires periodically. Another reason why the spark plug wire might have to be replaced is when it is being pulled off of the plug and the connection to the spark plug stays on the plug. This occurs since the polymer boot at the end of the wire has adhered to the plug.