What Spark Plug To Use For Your Lawn Mower

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Gasoline engines need a spark plug, and that includes your lawn mower. So, it’s important that you find the right spark plug for your mower so that you can mow your lawn properly and without any issues.

To help you find the right spark plug, we’ve created this guide so you can make sure you have the right one for your lawn mower. We’ll tell you everything you need to know about spark plugs and which one you need for your lawn mower.

What Is A Spark Plug?

The compressed air-fuel mixture is ignited by the spark plug during the combustion stroke of gasoline engines, producing a blast that releases energy.

A spark plug is required to ignite the air-fuel mixture in a lawnmower’s gasoline engine, just like in a vehicle.

Lawn mower engines are made to work with spark plugs of a specific size. You can experience some problems if you try to use the incorrect spark plug in your lawn mower.

Some of the most significant issues that might occur are the engine misfiring, the engine not starting, the engine running loudly, being unable to screw the spark plug in, oil fouling on the threads or tip of the spark plug, or the spark plug overheating and breaking.

It is important to note that not all lawn mowers use a spark plug that is one size. In light of this, spark plugs used in lawn mower engines often come in a range of sizes.

The threads on a spark plug are used to measure it. Thread size and thread length are the two thread characteristics that can differ on a spark plug.

The heat rating is the last distinction between spark plugs after this. Varying spark plugs have different operating temperature ratings. 

You will definitely be able to go through the parts aisle a little more efficiently if you have a basic understanding of how spark plug sizes are determined. Here is some further information concerning these three qualities:

Thread Length/Reach

A spark plug’s reach or length determines how long it is and how deeply it will be seated in the engine. There is a larger variety of thread lengths, and choosing the right one is essential.

Your spark plug may start building up fuel or oil at the tip if it is not seated deeply enough. Overheating and oil/gas accumulation on the threads can happen if the spark plug is screwed in too far.


Thread pitch and thread diameter are the two measurements that make up a spark plug’s thread size. The space between each thread is measured as thread pitch. 

This distance, which is measured in millimeters, is extremely small. On the other hand, thread diameter is a measurement of the breadth of the spark plug’s threaded portion.

Heat Rating

Spark plugs are made to withstand a specific amount of heat as different engines operate at various temperatures. A standardized rating on a scale from 2 to 12 is used to describe this. 

The spark plug will heat up more quickly the lower the number. In comparison to a spark plug with a heat rating of 8, a spark plug with a heat rating of 6 will overheat at a lower temperature.

What Spark Plug To Use For Your Lawn Mower

When To Change Your Spark Plug

There are a few things you should look out for to determine whether or not your spark plug needs replacing. These could be:

  • Excessive fuel consumption – One of the most common indications of a defective spark plug is excessive oil consumption.
  • Distorted appearance – If the spark plug has been damaged in any way, it can be physically examined to determine this. Any damage to the flat top, electrode, gap, or metal cap may make it inoperable.
  • Poor engine performance – The engine won’t operate as smoothly as it should if the spark plug isn’t functioning properly. It will need to be cranked again in order to start.

Finding The Right Spark Plug

Lawn mower spark plug sizes are standardized in a few ways, just like they are for motorcycles and cars. You’ll discover that their thread pitch, diameter, and reach all fall within a similar range.

With this information in mind, these spark plug thread measurements are typically the right size for these types of lawn mowers:

  • Riding mower – 1 to 1.5 mm pitch, 12 to 14 mm diameters, and 15 to 19 mm reach.
  • Push mower – 1 to 1.5 mm pitch, 10 to 12 mm diameter, and 8 to 12 mm reach.

The best advice we can give is to check your owner’s manual if you’ve looked at the typical lawn mower spark plug sizes but are still unsure of how to go about getting the plug you need.

It is generally a good idea to ask the manufacturer for information.

However, if you’ve lost your manual or purchased a used mower without one, you have a few more options.

You can either check the component number written on the spark plug itself or take your spark plug to a hardware store and ask for assistance.

We advise bringing your old spark plug with you when replacing it to ensure that the new one is the exact same size.

Where To Buy A Spark Plug For Your Lawn Mower

Spark plugs are one of the most sold engine parts. You can purchase a replacement spark plug for your engine for as low as three or four dollars.

They are primarily sold in stores and businesses that sell engine components. The usual locations where combustion engines are sold are where you can find them.

Find a store that sells lawn mowers, and they should also sell engine parts, which must contain spark plugs. Spark plugs are also sold at online retailers, but in order to choose the right one, you must know what you’re looking for.

Final Thoughts

Making sure you have the right spark plug is essential to the smooth running of your lawn mower. With this guide, you’ll be able to determine what size spark plug you need and start mowing your lawn with confidence.

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