What is the normal spark plug gap?

[LaLydia]

The normal spark plug gap is between 0.6 to 1.3mm. The larger the spark plug gap, the longer the arc generated during ignition, making it easier to ignite the air-fuel mixture in the cylinder, resulting in greater kinetic energy. However, a larger gap requires higher voltage to penetrate the air during ignition, so different engines are matched with spark plugs of varying gap sizes. Commonly known as spark plugs, their function is to discharge the high-voltage pulses sent through the ignition wires, penetrating the air between the two electrodes to generate a spark, thereby igniting the air-fuel mixture in the cylinder. The main types of spark plugs include: standard spark plugs, extended tip spark plugs, electrode spark plugs, seat-type spark plugs, surface gap spark plugs, and surface discharge spark plugs. Spark plugs work in conjunction with the ignition system and fuel supply system to enable the engine to perform work, collectively determining the engine's performance to a large extent.

[LolaDella]

Last time I changed spark plugs, I did some research on this. The normal gap should be between 0.7 and 1.0 millimeters. My old Toyota uses a 0.8mm gap, while my neighbor's German car has a 0.9mm gap. This number is particularly important - too small and it leads to insufficient ignition energy, too large and it might not fire at all. I've measured it several times with a feeler gauge and found that after about 30,000-40,000 kilometers, the gap increases by roughly 0.1mm. If you experience hard cold starts or jerky acceleration, it's likely due to incorrect gap. Now I check them every 30,000 kilometers - carefully adjusting the side electrode with professional tools, as being too forceful can break the ceramic part. For new cars, there's no need to adjust them yourself as they come properly set from the factory.

[MacAustin]

The mechanic told me that the spark plug gap is generally within the range of 0.7 to 1.0 millimeters. Japanese cars commonly have a gap of 0.8 mm, while German cars mostly use 0.9 mm. Never try to adjust the electrode gap by hand—always use a feeler gauge for precise measurement. If the gap is outside this range, the car will run noticeably poorly. A gap that's too large means the ignition voltage can't keep up, causing hesitation during acceleration; a gap that's too small results in weak sparks and increased fuel consumption. The most common issue is carbon buildup narrowing the gap, which can be cleaned with a small blade. I've seen cases where dropping a new spark plug on the ground caused an excessive gap, rendering it useless. It's recommended to have the mechanic check the gap when replacing spark plugs every 40,000 kilometers.

[ReaganDella]

The normal spark plug gap is 0.7-1.0 mm. If the gap is too small, the ignition energy will be weak, gasoline won't burn completely, and the exhaust pipe is prone to blackening and emitting black smoke; if the gap is too large, higher voltage is required, and it may not ignite at all. Iridium spark plugs usually have a preset gap of 0.8 mm. I've replaced a set, and they do run smoother than nickel alloy ones. When adjusting, you must use a disc-shaped gap gauge - don't try to make do with a coin. Remember that the electrode bending angle shouldn't exceed 15 degrees, otherwise it will affect the ignition position. Also pay attention to the spark plug installation torque - too tight and you might crush the ceramic body. I always recheck the gap with a vernier caliper during my 20,000 km inspections.