Are Lawn Mower Spark Plugs Universal?

As an Amazon Associate, this site earns commissions from qualifying purchases. For more information click here.

Lawn mowers need a spark plug to generate the spark that will ignite the piston fuel mix. This is necessary to start the engine. It goes without saying that these components are essential for lawn mowers. So it is only fair to ask if lawn mower spark plugs are universal. Can you use any type of spark plug or is a specific type needed by these engines?

Lawn mower spark plugs are not interchangeable. Each engine only works with a specific type of spark plug, and using one that is not compatible with your lawn mower can cause damage.

How Do I Know Which Spark Plug For My Lawn Mower?

Each lawn mower has a specific engine number (not to be confused with serial numbers or titles), and this tells you what type of spark plug it is compatible with. Incompatible spark plugs will not fit, and forcing can cause slow down or halt operation.

The simplest way is to take the old spark plug to a lawn mower parts store. Show them the spark plug and the vendor should be able to provide the correct replacement. You can also go to the manufacturer site for specific information on what spark plugs to use.

First you have to remove the spark plug from the engine. Take off the rubber cap and wire atop the spark plug. Use a wrench to unscrew the spark plug.

If you look at the plug ceramic insulator, you will see numbers printed on it. Writ this number down and show it to the mower store personnel. Either that or bring the spark plug with you. Whichever you choose, the vendor will get you the right spark plug.

If you lost the spark plug, note down the lawn mower make as well as its engine model number. You will find the model number somewhere on the side of the engine block. Provide this information to the store, or use it to order a new spark plug online.

Rider vs. Push Lawn Mower Spark Plugs

Most rider mower spark plugs are 12-14mm in diameter with a 1.1-5mm pitch. Push or walk behind lawn mower spark plugs have a diameter of 10-12mm and a 1-1.5mm pitch.

Rider mowers. Riders and lawn tractors require heavy duty spark plugs. Most of them run on 13-30 HP engines so durability is a must. You should be able to find a suitable spark plug in any well stocked lawn mower parts store. Or you can go online and order a replacement.

All you need is the engine model number and you can buy a new spark plug from the manufacturer site or other companies.

Push lawn mowers. Push and walk behind lawn mowers are available as 2 or 4-stroke engines. In both cases you will need a side valve or L-head spark plugs. These are smaller compared to most car spark plugs, so buy only if you are certain it is for lawn mowers. Our pick is the Sun Joe MJ500M for its reliability.

Image Credit: Fanmartin

These spark plugs are constructed from various materials. Copper is the most affordable, the most common and also the weakest. Iridium and platinum spark plugs are the most expensive and will last the longest.

In most instances though, a copper spark plug is enough. Unless you have a really large lawn that requires hours and hours of maintenance every day, cheap spark plugs will be sufficient.

When Should You Replace Lawn Mower Spark Plugs?

Most manufacturers recommend replacing the spark plug after every 25 hours of use. However you may also install new spark plugs at the start of every season.

If you are not sure, consult your owner’s manual and follow the recommendation given there. If there is nothing in the manual, just choose between every 25 hours or before each new season starts, whichever comes first.

But if there are problems with the spark plug, you should replace it immediately. Signs of a faulty spark plug are unusual engine noise, not turning over, stalling or refusing to start. If you notice one or more these in your mower, turn it off and check the engine right away.

Look carefully and thoroughly at the spark plug. If it is just dirty, a quick clean up may be enough. If there is oil all over it LNK you have to check the rest of the engine. Get a new spark plug right away if there is any crack.

Remember that the “replace every 25 hours” is a guideline, not a rule. That advice, along with the “get a new spark plug at the start of each season”, assumes your lawn mower sees average use. If you have the PROYAMA 196cc lawn mower for instance, its components last longer.

If you mow your lawn occasionally, its spark plug will last longer than 25 hours. You might even be able to use it for more than one season. The opposite is also true. If the lawn mower is used heavily, it might be better to buy a new spark plug more often.

What If You Use the Wrong Spark Plug?

Installing the wrong spark plug can damage the engine. Even if you get your lawn mower to run, it will be less fuel efficient. An incompatible spark plug can also result in incorrect fuel combustion.

The end result is poor performance. Even if you have powerful, heat treated mower blades, it will not mow grass properly. Without the right spark plug, the engine does not have enough power to perform this task. One or more cylinders will not run, depriving the mower of power.

Lawn mower spark plugs only work with specific types of engine models. The plug gap allowance, size and other specifications must all be considered when buying a replacement.

The bottom line is you should always use the right spark plug for your lawn mower. As explained earlier, there are many ways to find out what spark plug size is the correct one for your mower model. There is no reason not to use it and there are a lot of potential problems that can come up if you install the wrong one.

Frequently Asked Questions

Are lawn mower spark plugs the same?

No, lawn mowers use specific types of spark plugs for a particular engine. Manufacturers utilize different methods to crate their engines, which requires the use of particular spark plugs. For each engine model it will only work with a unique type of spark plug.

Where do I find spark plug replacements?

Any good hardware store will have spark plugs for the most common lawn mowers. You can also order from the manufacturer website online. Not that lawn mower engine makers are usually different from that of the lawn mower itself. Check the owner’s manual so you will know where to order spark plugs.

What spark plug do I need for a Briggs and Stratton?

For most of their lawnmowers, the 496018S will be fine. This works with most, but not all models. If you are not sure, consult your owner’s manual.

Will a bad spark plug cause a lawn mower not to start?

A lawn mower will not start with a broken spark plug. If the spark plug is not damaged but dirty, the engine might start. But it will stall and run poorly. The best solution is to clean it, and if that does not work, buy a replacement.

How do I know if my lawn mower spark plug is bad?

The most common symptom of a faulty spark plug is an engine that refuses to start or misfires. Another sign is low power: the mower starts but runs poorly. A damaged spark plug will also require you to pull harder to make the lawn mower start.

Lawn mowers running on damaged spark plugs lose fuel quickly too. When the spark plug is damaged, fuel efficiency is compromised and must be replaced quickly.

Should my 4-stroke lawn mower spark plug have oil?

No, it should never have oil. If it does, turn the mower off and inspect the engine. If everything is all right, clean the spark plug and try again.