There are mainly four kinds of spark plug in the market according to the electrode material, that is, nickel alloy, platinum, iridium, double iridium spark plug. Of these materials,double iridium ranks the best, nickel alloy the last. Iridium is a kind of very hard precious metal with the highest melting point as high as 2,454 degrees. The center electrode of the iridium spark plug is made to be extremely small, allowing for more concentrated ignition and greater energy production. Generally speaking, iridium or platinum spark plug is a good choice for its good price performance ratio. But you should buy the genuine products.
2. Calorific value ( or heat range)
Different manufacturers have different naming rules for the calorific value of the spark plug, so it can not be classified as "high" or "low" .But it can be simply divided into "cold type" spark plugs with good heat dissipation and "hot type" spark plugs for low-speed engines. For example, the higher number of champion spark plug, the hotter it is ; while the NGK and Matuwa (LSND) spark plug is the opposite, the higher, the colder. Normally the calorific value ranges from 5 to 13. Cold type is suitable for high-speed high compression ratio engine car. While hot type is for low compression ratio engines.
It includes the spark plug length,thread diameter, thread length and hexagon.To replace the spark plug, you have to choose the exactly right size, Even small differences in size can have a negative impact on performance, which can damage the engine. Each spark plug has its model number printed on it. For example, IBKR6ES, BK means the thread diameter is 14mm, E means thread Length is 19mm.
However, it is too difficult and meaningless for ordinary users to remember these models. Just remember your car model. It’s not difficult to find the corresponding item in manufacturers’ or suppliers’ product brochure.
In all , once the dimension and calorific value is same as the original, the spark plug will work normally. As for its performance and life, it depends on the material.