Is a Smaller Spark Plug Gap Better?

Have you ever wondered whether a smaller spark plug gap could improve your car’s performance? Auto enthusiasts continue to debate the distance between a spark plug’s center and ground electrodes and how it affects fuel efficiency and combustion power.
Let us delve into the topic and put an end to this ongoing debate once and for all.

So, is a smaller spark plug gap better? Most car manufacturers use smaller plug gaps to maximize fuel economy and combustion. However, the ideal spark plug gap size depends on several factors, including the vehicle’s make and model, engine characteristics, and planned use. There isn’t a one-size-fits-all answer to it.

What does Spark Plug Gap mean?

All You Need To Know About the Car Spark Plug

A spark plug gap refers to the distance between the center electrode and the ground electrode of a spark plug. The spark plug is a critical component of an internal combustion engine, and its main function is to ignite the air-fuel mixture in the combustion chamber by generating a spark across this gap.

The size of the gap directly affects the performance and efficiency of the engine. If the gap is too small, the spark may not be strong enough to properly ignite the air-fuel mixture, resulting in poor combustion and reduced engine performance. Conversely, if the gap is too large, the spark may not be able to jump across the electrodes, causing misfires or a failure to start the engine.

Spark plug gaps are usually specified by the engine manufacturer and can be found in the owner’s manual or on a label under the hood. It is essential to maintain the recommended spark plug gap to ensure optimal engine performance and fuel efficiency. The gap can be adjusted using a spark plug gap tool or a feeler gauge.

The spark plug gap may look like little, but it plays a huge part in sparking the fire that drives your car!  Consider it as the Grand Canyon for your engine. A tiny spark leaps over the gap between the spark plug’s center and ground electrodes to ignite the fuel-air combination and start the explosion that drives your car forward.

However, there’s still more! Precision is more important than mere size when setting the plug gap. It is similar to finding your engine the ideal dancing partner. If the gap is too tiny, the spark can find it difficult to jump, which might cause misfires and poor performance.

Importance of the correct Spark Plug Gap

How To Gap Spark Plugs | Champion Auto Parts

A correctly adjusted spark plug gap ensures a reliable spark, which results in complete combustion and excellent engine performance. Therefore, the spark plug gap is essential for the proper functioning and efficiency of an internal combustion engine.

The gap directly affects the ignition of the air-fuel mixture, which in turn influences engine performance, fuel efficiency, and emissions. Here are some reasons why precisely adjusting the spark plug gap is important:

Engine performance: A correctly set spark plug gap ensures a strong and consistent spark, providing a complete burn of the air-fuel mixture. This leads to optimal combustion, resulting in better engine performance, power, and responsiveness.

Fuel efficiency: Many car owners place a high priority on fuel economy, and the spark plug gap has a direct bearing on this element of engine performance. A precise plug gap guarantees the practical and waste-free burning of gasoline.

When the air-fuel mixture is ignited efficiently, the engine uses fuel more effectively, resulting in better fuel economy. An incorrect gap can lead to incomplete combustion, which wastes fuel and reduces fuel efficiency.

Emissions: Proper ignition of the air-fuel mixture reduces the production of harmful emissions, such as unburned hydrocarbons, carbon monoxide, and nitrogen oxides. An incorrect spark plug gap can increase these emissions, contributing to air pollution and potentially failing emissions tests.

Engine longevity: A properly gapped spark plug ensures smooth engine operation, reducing stress on engine components and prolonging their lifespan. Incorrect gaps can lead to misfires, knocking, or pre-ignition, which can cause damage to the engine over time.

For instance, knocking happens when the air-fuel combination ignites too quickly in the combustion chamber, causing a knocking noise and damaging the engine. Such problems may be avoided, and smooth, efficient combustion ensured with a correctly regulated spark plug gap, leading to increased engine performance and lifetime.

Reliability: A precise spark plug gap minimizes the risk of engine misfires or failure to start, ensuring the reliable operation of the vehicle. It also encourages a continuous and stable spark, which results in less vibration and better engine running.

Engine vibrations can increase wear and tear on engine parts, resulting in early failure and poor engine performance.
A correctly adjusted spark plug spacing also helps support a steady idle by preventing the engine from stalling or surging at idle. A smoother and more reliable engine performance leads to a more pleasurable driving experience.

To maintain these benefits, it is crucial to regularly inspect and replace spark plugs as needed, keeping the gap within the manufacturer’s recommended specifications. Always consult your vehicle’s owner’s manual or a qualified technician for the correct gap settings and spark plug replacement intervals.

Signs Of Improper Spark Plug Gap

An improper spark plug gap can cause several issues in a vehicle’s performance, as the gap between the central and ground electrodes plays a crucial role in the combustion process. When the gap is either too wide or too narrow, it can lead to various symptoms. Here are some common signs that may indicate an improper spark plug gap:

Rough idle: If the spark plug gap is incorrect, the engine may experience an uneven or rough idle. This can be felt as the vehicle vibrates or shakes while idling, indicating that the combustion process is not occurring smoothly.

Misfires: An improper spark plug gap can cause misfires, which occur when the air-fuel mixture in the cylinder fails to ignite properly. This can result in a loss of power and poor fuel efficiency, as well as potentially damaging the catalytic converter.

Reduced fuel efficiency: A suboptimal spark plug gap can negatively impact the combustion process, leading to incomplete burning of the air-fuel mixture. This can cause reduced fuel efficiency as more fuel is consumed to maintain the same level of performance.

Poor acceleration: If the spark plug gap is incorrect, it can cause the engine to struggle during acceleration. You may notice sluggish or hesitant acceleration, especially when the engine is under load, such as during uphill driving or when carrying heavy cargo.

Difficulty starting: An improper spark plug gap can make it harder for the engine to start, especially in cold weather. This is because a smaller or larger than optimal gap may require more energy to create a strong enough spark for ignition.

Engine surging or hesitating: An incorrect spark plug gap may cause the engine to surge or hesitate during operation. This can be experienced as a sudden increase or decrease in power, making the vehicle difficult to drive smoothly.

Check engine light: The vehicle’s onboard diagnostic system may detect issues related to an improper spark plug gap, such as misfires or poor combustion. This can cause the check engine light to illuminate, indicating that there is a problem requiring attention.

Increased emissions: An improper spark plug gap can lead to incomplete combustion, which in turn results in increased exhaust emissions of dangerous pollutants, including carbon monoxide, hydrocarbons, and nitrogen oxides. This can cause your vehicle to fail an emissions test or contribute to increased air pollution.

If you notice any of these symptoms, it’s essential to check the spark plug gap and adjust it according to the manufacturer’s specifications. This can help restore optimal engine performance and prevent potential damage to other components.

How To Perfectly Gap Spark Plugs (Step-By-Step)

Gapping spark plugs correctly is essential to ensure optimal engine performance and efficiency. Here’s a step-by-step guide to help you perfectly gap your spark plugs:

Step 1: Gather necessary tools and materials:

You will need some specific tools to gap the spark plugs perfectly. The tools are:

  1. Spark plug gap tool
  2. New spark plugs (if you are placing new ones)
  3. The vehicle owner’s manual contains the gap size recommendations from the manufacturer

Step 2: Prepare The Gap Tool And Inspect Spark Plugs

Utilizing the spark plug gap tool, set the gap to the proper size as per the manufacturer’s recommendations. The gap size is often expressed in inch-thousandths.

Check the new spark plugs for any damage or flaws if you are replacing them. Examine them for any damage or defects, such as cracked insulators or bent electrodes. Ensure that they are the appropriate type and size for your car.

Step 3: Remove The Old Spark Plugs

Park the vehicle on a level surface and make sure the engine is cool to avoid burns or damage. Use a spark plug socket and ratchet to gently remove the old spark plugs if you need to replace them. When removing the electrode, exercise caution to avoid damaging the threads.

Step 4: Check the existing gap and adjust the gap if necessary

Using the spark plug gap gauge or tool, measure the gap between the central and ground electrodes of the new spark plugs. If it’s already within the specified range, no adjustment is needed.

If the gap is too small, use the gap tool or gauge to gently pry the ground electrode away from the central electrode until the desired gap is achieved. Be careful not to apply excessive force, as this could damage the plug.

If the gap is too large, use the gap tool or gauge to gently tap the ground electrode closer to the central electrode. Make sure to support the central electrode while doing this to prevent damage. Re-check the gap after making adjustments to ensure accuracy.

Step 5: Apply anti-seize compound and dielectric grease (optional)

Apply a small amount of anti-seize compound to the spark plug threads to facilitate easier removal in the future. Avoid getting the compound on the electrodes.

Apply a thin layer of dielectric grease to the inside of the spark plug boot to prevent moisture and dirt buildup, as well as to promote better electrical conductivity.

Step 6: Install the gapped spark plugs

Carefully thread the spark plugs into the engine by hand to avoid cross-threading. Once they are hand-tight, use a torque wrench and spark plug socket to tighten them to the manufacturer’s specified torque. Over-tightening can damage the spark plug or the cylinder head.

Step 7: Start the engine and test the performance

If you must removed ignition coils or wires to get to the spark plugs, reconnect them and return them to the correct sequence.  Now start the engine and let it idle, checking for any unusual sounds or vibrations. Take the vehicle for a test drive to ensure smooth acceleration and overall performance.


By following these steps, you can ensure that your spark plugs are gapped correctly and contribute to optimal engine performance. Remember to consult your vehicle’s owner’s manual for specific instructions and specifications, as they may vary by make and model.

Wrapping Up

The correct spark plug gap significantly impacts how well an engine performs. While the issue of whether a smaller vehicle plug gap is preferable or not is still up for dispute, it’s crucial to consider the engine’s particular needs.

To guarantee optimum engine performance and guard against potential problems, it is crucial to adhere to the manufacturer’s instructions and get advice from a licensed mechanic.

Spark plug lifespan may be increased, and combustion efficiency can be improved with routine spark plug maintenance and inspection, which includes checking and correcting the gap.

The ideal ratio of a smaller or bigger gap relies on various elements, including the engine’s design, fuel type, ignition system, and the vehicle’s intended use. Prioritizing optimum spark plug gap settings is essential for promoting dependable and effective engine performance.

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Mahir Ahmed


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