The NGK Standard Spark Plug is constructed from durable material that is corrosion and abrasion-resistant. The spark plug insulators are made of 99 per cent pure alumina silicate, providing longer insulator noses for reduced fouling.

The main differences between the STIHL NGK spark plug (right) and the off the shelf NGK plug (left) are:

The union nut (1) of a STIHL spark plug is fixed in place. This ensures there is no spark gap which could impair performance or potentially ignite gasoline fumes. Air (atmospheric) pressure and cylinder pressure decrease as altitude increases. As a result, spark plug tip temperature will also decrease. A colder heat range spark plug may be necessary due to the increased cylinder temperature as boost pressure (manifold pressure) and subsequent cylinder pressure and temperature increase.

A hotter heat range spark plug has an insulator design with a longer heat flow path to the metal shell of the plug. As a result, more heat stays in the ceramic firing end and less is dissipated to the engine. A colder heat range spark plug has an insulator design with a shorter heat flow path to the metal shell of the plug. As a result, less heat stays in the ceramic firing end and more is dissipated to the engine. For a spark plug to function properly, it must have a tip temperature high enough to burn off carbon deposits (self-cleaning) and avoid fouling, while remaining low enough to avoid overheating the ceramic firing end and pre-ignition.

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The spark plug firing end temperature must be kept low enough to prevent pre-ignition, but high enough to prevent fouling. This is called “thermal performance,” and is determined by the heat range selected. If the engine is to be operated at high RPM, under a heavy load or at high temperatures for long periods, a colder heat range may be needed. NGK is the brand leader in the UK spark plug market and are the world's biggest supplier to many major car manufacturers. Each and every one of their products are designed to meet the most rigorous standards and are the professionals' choice because of their quality and technical excellence. Their plugs can be found in use by teams in F1, WRC and MotoGP. Put simply, NGK genuine spark plugs are the workhorse at the heart of smooth-running engines around the world. SKU: PLCMR6HX Category: Spark Plugs Tags: 0000-400-7009, 0000-400-7011, 100, 101, 110, 130, 131, 168652-4, 31916-Z0H-003, 3365, 345FR, 439, 526XP, 531008615, 545, 545FX, 545FXT, 545RX, 545RXT, 550XP, 550XPG, 555, 556, 560XP, 560XPG, 562XP, 562XPG, 574519601, 6778, 90119, A425000040, BG56, BG66, BG86, Bosh, BR200, BR500, BR550, BR600, BR700, BT131, Champion, CMR6H, CMR6H-SLDCAP, CS2252, CS2253, CS2258, CS2260, CS2260WH, FC100, FC110, FC56, FC70, FC90, FC95, FR130, FR410, FR460, FR480, FS, FS100, FS110, FS111, FS130, FS131, FS240, FS25, FS260, FS310, FS311, FS360, FS40, fs410, FS460, FS460 C-EM, FS50, FS56, FS65, FS70, FS87, FS89, FS90, FS91, FS94, GX25, HL100, HL90, HL91, HL94, HL95, Honda, HQT-3, HS46, HS46 C-E, HS56, HS56 C-E, HS81, HS82, HS86, HS87, HT100, HT101, HT102, HT103, HT130, HT131, HT132, HT133, HT56, Husqvarna, Jonsered, KM100, KM110, KM111, KM130, KM131, KM56, KM90, KM94, Makita, MS 201 T, MS 201 TC, MS150, MS150 C-E, MS170, MS171, MS180, MS181, MS181 C, MS192 C-E, MS193C, MS193T, MS201, MS211, MS211 C, MS231, MS241, MS241 C-M, MS251, MS362, NGK, Plug, RZ7C, SH200, SH56, SH86, Shindaiwa, Spark, SR200, Stihl, T2600, T435, T540XP, USR4AC Related products This spark plug features a triple gasket sealing process that eliminates fuel leakage. It also comprises a solid copper core that gives superior heat dissipation and conductivity.

Excessively rich air-fuel mixtures can cause the plug tip temperatures to decrease and carbon deposits to accumulate, possibly causing fouling and misfires. The spark plug heat range has no relationship to the electrical energy transferred through the spark plug. The heat range of a spark plug is the range in which the plug works well thermally. The heat rating of each NGK spark plug is indicated by a number; lower numbers indicate a hotter type, higher numbers indicate a colder type. Fouling can occur more easily if the air-fuel mixture is not adjusted to compensate for the altitude. Higher altitude = less air = less fuel. The heat range must be carefully selected for proper spark plug thermal performance. If the heat range is not optimal, then serious trouble can be the result. The optimal firing end temperature is approximately 500°C (932°F) to 800°C (1472°F). The two most common causes of spark plug problems are carbon fouling (< 450°C) and overheating (> 800°C).

Pre-ignition will dramatically raise the cylinder temperature and pressure, which can melt and hole pistons, burn valves, etc. When the spark plug firing end (tip) temperature exceeds 800°C, pre-ignition originating from the overheated insulator ceramic can occur.