The gasoline internal combustion engines need the Mercedes-Benz Spark Plug Wires so the ignition of the fuel and air mixture can occur. For each cylinder there is an equal but separate spark plug wire on your Mercedes-Benz engine.
For the older Mercedes-Benz models, the spark plug wires are connected to the distributor cap. On the new models with the latest fuel injection system on them the wires are directly connected to the ignition coil. The older versions used the copper core wires while the newer models need the high efficiency of the glass fiber core spark plug wires. The glass fiber core wires transfer the electrical impulses at the speed of light, literally.
Both types of wires do wear out in time. The copper core loses their ability to transfer the electrical impulse and the resistance to this transfer of energy increases with time. The glass fiber cores become brittle in time from exposure to the heat of the engine compartment this causes the fibers to break increase the resistance to the transfer of energy to the spark plugs. In either case on or about the fifth tune-up the Mercedes-Benz spark plug wires should be replaced on your engine.
If as the owner of the Mercedes-Benz, you are conducting your own tune-up, be sure to take one precaution when removing the spark plug wire from the plug. This is to twist the boot that is covering the plug slightly. This will break the seal the polymer has made with the plug that is causes by the heat. If the wire is just pulled, in most intakes it will become disengaged from the end of the wire causing the need for it to be replaced.