The average life of spark plugs depends on a number of factors: mechanical condition of the engine, type of fuel, driving conditions and driver skill. Although a standard factory spark plug will last a significant amount of time, extended life can be achieved on some engines by using platinum tipped spark plugs. Decide for yourself whether there is a benefit from the additional costs.
When removing candles, check their condition. The condition of the spark plugs is a good indicator of the condition of the engine. Slight coating of light yellow or gray material (or rust red with unleaded fuel) on spark plugs that have been used for some time should be considered normal. Any other color, or an abnormally large amount of plaque, indicates something is wrong with the engine.
Gap between center and side (earthy) electrodes during normal operation increases slightly.
When the spark plugs are functioning properly, or more specifically, when the spark plugs are installed in an engine that is functioning properly, the spark plugs can be removed, cleaned, gap adjusted, and reinstalled in the engine without any harm to engine performance. This is acceptable for some improvement in the operation of candles, or, in extreme cases, (for example, when there is nothing to replace), but new spark plugs are always preferable.
In case of clogged candles (no normal spark), you need to find the reason (or source) dirt, remove it, and clean or replace the spark plug. Replacement is always recommended if possible.
The different spark plugs suitable for use in your engine are designed to operate over a variety of temperature ranges. The amount of heat absorbed by the candle is determined by the length of the lower insulator. The longer the insulator, the higher the temperature the candle will operate; the shorter the insulator, the lower the temperature. Spark plugs that absorb little heat and remain too cold when operated will accumulate lead, oil, and carbon deposits because they are not hot enough to release (desorb) this raid. All this leads to contamination of the candles and, consequently, to poor ignition performance. Spark plugs that absorb too much heat will not build up deposits, but the electrodes will wear out too quickly and, in some cases, overheating can lead to pre-ignition.
Pre-ignition occurs when the tips of the spark plugs become so hot that they ignite the mixture of air and fuel before a spark actually occurs. Pre-ignition usually causes a knocking sound at low speed and heavy load. In the most severe cases, the heat can become large enough to cause the air/fuel mixture to burn throughout the combustion chamber, not just the front of the spark plug. In this case, the explosion will be strong enough to damage the pistons, rings and valves.
In most cases, the manufacturer's recommended temperature range is correct; it is selected to ensure normal operation over a wide range of operating conditions. However, if the majority of your travel is long distances and high speeds, then you may want to set your spark plugs one step colder than the recommended standard. If the largest number of trips are short with a variety of modes (start-stop type), When the engine may not always reach operating temperature, a hotter spark plug can help burn off the deposits that normally build up under these conditions.