Feeler Gauge vs Gap Gauge, Which Is Better? [Video]

I use both the feeler gauge set and spark plug gap gauge to gap spark plugs but I have a preference. Which one is it? Read on.

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Maintaining the correct gap between spark plug electrodes is crucial for the optimal performance of spark plugs. You can use two most common tools to gap spark plugs; a feeler gauge set or a gap gauge. But one is definitely better, which one is it?

In this article, I compare these two spark plug gapping tools to see which is more suitable for the job. But that’s not all – I have also gone a step further to create a video demonstrating how to use both tools to gap spark plugs. This video will help you choose better between the two precision tools.

Gapper Tool vs Feeler Gauge; Which One Is Better For Gapping Spark Plugs? [Video]

In this video, I compare a spark plug gauge with feeler gauge. I also demonstrate how to use both tools to gap spark plugs so that you decide which one is the better fit for your needs.

Feeler Gauge vs Gapping Gauge

Feeler Gauge vs Gapping Gauge

Before we look at the differences between these two gapping tools, let me start with a brief definition of each of them.

What is a feeler gauge?

A feeler gauge is a precision measuring tool that consists of a set of thin metal blades or leaves of varying thicknesses. Hence the name thickness gauge. Each blade is marked with its thickness size in metric or standard units or both. These blades are typically bound together at one end, forming a stack.

To effectively measure a gap with a feeler gauge, you select the appropriate blade (or set of blades) from the stack that fits snugly into the gap. The size of the gap is equivalent to the sum of the thicknesses marked on the blades you use.

For instance, if you use a single blade, then then the width of the gap is equivalent to the size marked on the blade. And if you use two or more feeler gauge leaves, you determine the thickness by adding together the thickness sizes of each of the blades.

Check out this article to learn more about feeler gauges including some of the best options in the market.

What is a gapper tool?

A gapper tool or spark plug gap tool is a small disk made of sturdy metal. It has a stepped edge of different thicknesses. Some gappers, however, have wire loops or notches of specific thicknesses. Others have different shapes such as square and rectangular. But despite the shape or style, all gapper tools do one job only; gapping spark plugs.

Gapper tool Vs Feeler gauge

A major difference between a gapper tool and feeler gauge is that feeler gauges are more versatile. You can use a feeler gauge set to measure small gaps in a variety of mechanical and automotive applications whereas a gapper tool is only useful for gapping spark plugs.

That being said, a gapper tool offers more value than a thickness gauge when gapping spark plugs. Not only does it measure the spark plug gap but also has an in-built feature for expanding the gap. It has a small hole that is designed for prying the ground electrode of a spark plug to expand the gap.

gapping spark plug with gapper tool

Another advantage of a gap tool is that it is compact and easy to carry around. You can attach it to your keyring and have it at hand all the time. A feeler gauge set is also compact and easy to carry but you cannot carry it as casually as a gap gauge. It needs to be in a toolbox.

As far as measuring gaps is concerned, I like the feeler gauge because it feels more accurate. The only downside of using a feeler gauge to gap spark plugs is that you need two additional tools; a thick blade for expanding the gap and a hammer for tapping the electrode to reduce the gap. With the gapping tool, you only need a hammer for tapping the ground electrode if the spark plug gap is wider than you need it.

But the good thing is that both the feeler gauge and gapper tool are inexpensive. You can have both of them in your toolbox if you want versatility, speed, and precision. You can use a feeler gauge for adjusting valves, guitar setup, and other applications and a gapper for tuning spark plugs.


So, which one should you buy? Feeler gauge or gapper tool? Generally, I suggest that you get both tools because they are inexpensive. But if you just want to gap spark plugs, get a spark plug gap gauge. It will make your work easier. Otherwise, a feeler gauge might be a better choice if you want a versatile precision tool that you can use for other applications besides spark plug gapping.


Hey there! I am an field electrical engineer by day, a blogger by night, and DIYer on weekends. Throughout my career, I have used many tools and learned that getting the right tool for the job is the first step to getting the job done right. This is why I write about tools and tests/reviews them on this blog.

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