What are the effects of changing from spark plug heat range 6 to 7?
2 Answers
The effects of changing from spark plug heat range 6 to 7 are as follows: 1. The higher the heat range number of a spark plug, the cooler it is. If a vehicle originally uses a heat range 6 product but switches to heat range 7, there may not be significant operational issues. However, if the car frequently operates at low speeds, it is more prone to spark plug carbon buildup. 2. The heat range of a spark plug actually refers to an indicator of its heat absorption and dissipation capabilities. The amount of heat the spark plug itself dissipates is called the heat range. Heat ranges include numbers from 1 to 9, where 1-3 are low heat ranges, 4-6 are medium heat ranges, and 7-9 are high heat ranges. Original equipment manufacturer (OEM) spark plugs typically come in heat ranges 5, 6, and 7. The higher the number, the cooler the spark plug and the better its heat dissipation. There isn't a definitive answer as to whether heat range 6 or 7 is superior; the most reasonable choice depends on matching the heat range to the overall condition of the car's engine. 3. There may be slight impacts on vehicle fuel consumption, engine knocking, or engine horsepower. If the spark plug is too cool, it can lead to higher fuel consumption and carbon buildup in the combustion chamber. If it is too hot, it can cause knocking, reduced power, or engine overheating. A higher heat range means faster heat dissipation, which can lower the spark plug temperature and cause carbon buildup at the ignition point, leading to misfires. Conversely, a low heat range with insufficient heat dissipation can raise the spark plug temperature, causing pre-ignition (knocking) and potentially damaging the spark plug's ceramic insulator or melting the electrodes. Therefore, the heat range of a spark plug should not be changed arbitrarily.
As someone who frequently tinkers with cars, changing the spark plug heat range from 6 to 7 is no small matter. A heat range 7 spark plug dissipates heat faster and runs cooler, which sounds great—ideal for long drives in hot weather or turbocharged engines, as it can reduce pre-ignition issues. But after swapping, I noticed cold starts became particularly difficult, especially in winter. The engine would shake noticeably after ignition, and acceleration felt rough because the spark plugs weren’t hot enough to burn off carbon deposits. Over time, fuel consumption might even increase, putting extra strain on the engine. My advice? Don’t change it casually unless your car’s manual recommends it or the engine has been modified. I learned this the hard way—ended up spending time swapping back. Now, I stick to the factory heat range for peace of mind and safety, at least avoiding stalling or excessive carbon buildup. Regularly checking spark plug condition is the real key; this kind of modification is just too risky.
