How Spark Plug Gapping Works And Why It's Important

If you bought spark plugs, you may have been offered a spark plug gapper or been told, "These are pre-gapped." Let's dive into what they're talking about.

WHAT "GAP" ARE THEY TALKING ABOUT?

On a spark plug, there are two electrodes at the bottom, one ignites with electricity and grounds out on the other. The "gap" is the gap in between those two electrodes. Check out our cool diagram.

HOW DO I GAP THEM?

There are a few different tools, a common one is the "spark plug gapper" that most places that sell spark plugs also sell (pictured below). The end of that disc gradually goes up in thickness, you slide the spark plug into the gapping tool and slide it to your desired gap width. To reduce the gap, you can typically push down on the bottom (ground) electrode with your thumb.

WHAT DOES PRE-GAPPED MEAN?

Almost all spark plug manufacturers pre-gap spark plugs now, but this is usually just a typical gap, and your vehicle may require a different gap setting. Usually, a quick Google, the manual, or the dealer/auto parts store can tell you the recommended gap setting.