A spark plug is an electrical device used to ignite compressed aerosol gasoline by means of an electric spark, as its name suggests. It is usually found in the cylinder head of some internal combustion engines. These plugs have an insulated center electrode which is connected by also a heavily insulated wire to an ignition coil or magneto circuit on the outside. This then forms, along with a grounded terminal on the base of the plug, a spark gap inside the cylinder. Only some of the internal combustion engines use spark plugs(and these are called spark-ignition engines) because others use compression-ignition engine like that of diesel engines.

This plug as discussed above is connected to the high-voltage brought upon by the ignition coil or magneto. The electrons flow from the foil and thus a difference in voltage develops between the center and side electrodes. The current still wouldn't be able to flow here as the fuel and air in the gap is an insulator. However, as the high voltage rises further, the gases located between the electrodes change structure. And when the voltage exceeds the dielectric strength of the gases, the gases become ionized. This will then be the conductor for the electrons to be able to flow through the gap.

When the series of electrons cross the gap, it raises the temperature of the spark transmission to 60,000K. This intense heat makes the ionized gases to expand quickly, like that of a mini explosion. The click in this spark plug is similar to the lightning and thunder. The heat, together with the pressure, pushes the gases to react with one another. After the spark, a small ball of fire in the spark gap should be seen as this means that the gases are already burning on their own. The size of this fireball, however, is entirely dependent on the exact composition of the mixture between the electrodes and the level of combustion chamber turbulence at the time of the spark. This small fireball will make the engine run s though the ignition timing was related, and a large one as though the timing was advanced.

As mentioned before, spark plugs are found on spark-ignition engines and of the automakers who make use of the role spark plug play in internal combustion is the Swedish automaker Volvo. But however quality Volvo puts into their Volvo Spark Plugs, a wear and tear of it couldn't be avoided after a long time of usage. Its spark plugs may give in and this would cause a real problem to Volvo car owners. A probable result to failing Volvo Spark Plugs is a car running less efficiently. And if there is inefficiency in the running of the engine, there will also probably be less power for the Volvo, more gasoline will be used, and an increase in emission. In this case, a replacement for the Volvo Spark Plugs is only proper.