Torque and Gap- Critical to Spark Plug Performance

BROADVIEW, IL- August 11, 2014 – Installing spark plugs on late-model vehicles with high-tech engines requires precision and care.

Apply the proper torque

First, know the torque specification for that plug and using a torque wrench, tighten the plug to the proper foot pound of pressure. All Bosch Spark Plug packages, for example, specify a foot-pound torque rating that needs to be applied using a torque wrench.

Over-torquing or under-torquing a spark plug will affect engine performance.  While an under-torqued spark plug that is loose in the cylinder will allow combustion gases to escape from the engine, over-torquing can damage the components of the plug. Both conditions will result in loss of engine performance.

Ensure the correct spark plug gap

Second, make sure the spark plug gap is correct – that is, the distance from the center electrode tip to the ground electrode. If the gap is too small, the flame kernel will not grow leaving the air-fuel mixture unburned and affect engine performance and gas mileage. If the gap is too large, there won’t be enough electricity to create a spark, leading to a misfire. Many Bosch Spark Plugs come pre-gapped from the factory.



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In the U.S., Canada and Mexico, the Bosch Group manufactures and markets automotive original equipment and aftermarket products, industrial drives and control technology, power tools, security and communication systems, packaging technology, thermotechnology, household appliances, healthcare telemedicine and software solutions. For more information, please visit, and

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*Due to a change in legal rules governing consolidation, 2013 figures can only be compared to a limited extent with 2012 figures. Exchange rate: 1 EUR = $1.32812




This spark plug was over-torqued. The contact marks and cracking on the ceramic in-sulator show it was installed using an impact driver, not a torque wrench.
This spark plug was under-torqued. Because it wasn’t tight enough in the cylinder, the spark plug vibrated loose and allowed combustion gas deposits to form around it.