How to Gap a Spark Plug for Optimal Engine Performance

spark plug gap check

So, you’ve decided that it’s time to gap your spark plugs!

You probably just bought new plugs and you know they should be gapped. Or maybe you just bought an older car and had no idea that maintenance was required on that kind of level!

Now, after reading these instructions, you’ll feel confident in your ability to gap out your new spark plugs.

Your car has been running smoothly so far – but now it seems like it wants more power. So you head over to your local auto parts store and pick up some brand-new spark plugs; their packaging says they’re pre-gapped but that there is room for adjustment.

Simply follow these simple instructions to learn how to gap spark plugs properly, and ensure your engine operates at peak performance.

Why Gapping Spark Plugs

Spark plugs are one of many vital components of your engine. Their job is to ignite fuel in order to produce energy.

This powerful little device is responsible for powering everything from lawnmowers and snow blowers to backhoes and semi-trucks.

Knowing how to gap spark plugs will ensure that your engine can run as smoothly as possible at all times.

So what does gap mean?

When we say gap, we’re referring to a part of each spark plug called the electrode gap (the space between each individual prong).

The size of an electrode gap has everything to do with how well a spark plug performs within an engine.

Do Spark Plugs Always Have to Be Gapped?

Not exactly.

One of the most common misconceptions is that spark plugs always have to be gapped.

What I mean is, in modern cars, the spark plugs are often precisely set by the factory.

That said, it does pay off to spend five minutes with some basic tools checking and adjusting your gaps before firing up your engine for another 10,000 miles (or so).

However if you tuned your engine and it is running under more pressure, it is most likely that you will need to reduce the gap of your spark plug.

Check with your tuner for the proper gap.

We’ll take you through the how-to steps below.

Finding The Proper Gap 

Before you can gap your spark plug, you must first determine what size gap you should use. That’s because different engines will require different gap sizes in order to run properly.

The gap depends on your vehicle’s engine, but most are in the range of 0.028 to .060. Consult your owner’s manual for the right information.

How To Gap A Spark Plug?

  1. Carefully measure the gap on the spark plug with a feeler gauge, and take note of the gap’s measurement. Record the measurement, then compare it with your owner’s manual for the recommended setting.
  1. Use the spark plug gapping tool to adjust the gap. Gently bend the ground electrode in to narrow the gap or bend it out to widen it.
  1. Carefully adjust to within a fraction of an inch. Spark Plugs are durable but don’t withstand pressure, so avoid contact with the center electrode. If you snap off the grounding electrode or damage the center electrode while twisting, you will need a new spark plug. Precious metal iridium or platinum center electrodes are very fragile when you twist them. Using the right size spark plug gapping tool is crucial.

What Happen If Your Spark Plug Gap Is Incorrect

If your spark plug gap is too large, you might have problems with poor engine performance. Your car will run sluggishly and could suffer from misfires.

On top of that, you might actually decrease your gas mileage and increase emissions as well.

If you’re driving at high speeds or under extreme loads, you’ll probably notice other performance problems.

Spark plugs will wear out faster if they aren’t gapped properly.

You will even need to replace your spark plugs more often if they’re not gapped correctly in addition to paying more money on gas because of misfires and poor mileage; these are all costs that can add up quickly over time!


Gapping a spark plug can seem intimidating if you’ve never done it before, but it doesn’t have to be as hard as you think!

In fact, with some simple tools and a little know-how, you can get your engine running at peak performance in no time.

If you don’t feel comfortable gapping your own plugs, bring them into an auto repair shop and ask about their services. 

Gapping spark plugs is actually easy, so why not try doing it yourself?

It could save you money down the road when it comes time for service work or repairs.

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