What is the torque standard for spark plugs?
2 Answers
Spark plugs are one of the most important consumable parts in a car. The general installation torque for spark plugs is 25-30 N/m, which applies to mainstream spark plugs on the market with a thread diameter of 14 mm. Here are some precautions for replacing spark plugs: 1. Always purchase spark plugs of the appropriate size, which can be checked on the official website. 2. Disassembling and installing spark plugs requires corresponding professional tools. You can rent or borrow a set of tools and follow the torque corresponding to the spark plug size for disassembly and installation. Not all vehicle models use mainstream spark plugs. 3. Disassembling spark plugs is not a big problem, but it is essential to use the correct tools and methods. Avoid using brute force to prevent the spark plug from stripping or even falling into the cylinder.
When it comes to the torque specifications for spark plugs, having worked in auto repair shops for over a decade, I've noticed many people assume they're all the same—far from it. Each vehicle's engine design differs, and the required torque varies between aluminum and cast iron cylinder heads. I've seen numerous DIYers replacing spark plugs, either overtightening them (causing thread stripping) or leaving them too loose (resulting in air leaks that affect engine performance). Generally, standard spark plugs require about 25 N·m for cast iron blocks, while aluminum heads—being softer—need reduced torque around 15 N·m. The most reliable approach? Check your vehicle’s service manual—it spells it out clearly. If you lack the manual, err on the side of under-tightening and gradually increase torque rather than cranking it down in one go. Remember: a torque wrench isn’t decorative—a damaged cylinder head spells major trouble.