When it comes time to periodically inspect the car and replace various operating fluids, filters or spark plugs, we often face a dilemma, whether to use the materials indicated by the car manufacturer in the instruction manual, or to use a commercially available alternative.
The solution to this problem in the case of spark plugs is perhaps the simplest, because the type of candles specified in the factory manual is not only the result of tests and tests, but it is also the result of a commercial agreement between the car manufacturer and the candle maker. Users of older vehicles will certainly face the necessity to use a replacement for candles.
The largest manufacturers have introduced a wide range of spark plugs to the market, characterized by a semi-surface spark discharge. Surface discharge and semi-surface discharge candles have been known for years. What is new is the combination of two phenomena in one candle: traditional air discharge and sliding air discharge, which, however, do not occur simultaneously.
In cars operated in variable conditions, when short-distance driving and in traffic jams prevail, the spark plug insulator becomes rapidly contaminated with carbon build-up. Self-cleaning of the candle takes place only when driving for a long time, which usually does not happen in the city. Carbon deposits remaining on the candle weaken the spark, because it causes electricity leakage. This can lead to misfiring, manifested by difficulties in starting a cold engine, its uneven operation or damage to the catalyst. To remove these inconveniences, semi-surface combined discharge candles were designed for vehicles operated mainly in city traffic.