A spark plug works by taking a small electrical charge from the ignition coil and passing it through two electrodes. The difference in the charge at each of those electrode points creates a spark. That, in turn, ignites the fuel, and the engine runs.
In a riding mower, that spark happens several thousand times a minute, so it should be no surprise that spark plugs eventually wear out as the electrodes get sooted up or burn away. At first, the difference is so small it isn’t noticed, but eventually performance deteriorates. The mower becomes more difficult to start. Or worse, on the day you’re tidying up the yard for the first cookout of the summer, it won’t start at all. It coughs and splutters and maybe smokes more than usual, all of which are signs that it’s time for a change.
To help you decide which spark plug is right for your mower, keep reading to learn about many of the important features to consider. Also, check out the following spark plugs, which are some of the best on the market to use as replacements for riding mowers.
- BEST OVERALL: Champion Copper Plus 71 Spark Plug
- BEST BANG FOR THE BUCK: Maxpower 334058 Spark Plug For Riding Mowers
- UPGRADE PICK: E3 Spark Plugs E3.22 Lawn and Garden Spark Plug
- BEST PLATINUM: Briggs & Stratton 5062K Spark Plug Platinum
- BEST IRIDIUM: Fram Autolite XP5325 Iridium XP Spark Plug
What to Consider When Choosing the Best Spark Plugs
While it’s possible to replace an old spark plug with the same type or use the riding mower’s owner’s manual to figure out the best spark plugs to use, keep in mind that the manual includes the best spark plugs available at the time the manual was created. If the mower is a few years old, improvements in spark plug technology may make other options viable. The following information explains spark plug technology in detail so you can make an informed decision to purchase the best spark plugs for your riding mower.
The type of spark plug is usually defined by the material used in the electrodes: copper, platinum, or iridium.
- Copper is the best electrical conductor available for spark plugs. However, it is soft and has a low melting point, so wear rates can be high. To combat this, it is usually coated in a thin layer of nickel alloy. Copper spark plugs are the cheapest type, but they typically need to be replaced about once a season.
- Platinum is a much harder metal and more resistant to heat. They last up to four times longer than copper, but they are more expensive. Two types of platinum spark plugs are available. Single platinum models have a copper central electrode with a small circle of platinum welded on the end, while the other electrode remains copper only. On double versions, both electrodes have platinum end elements.
- Iridium (or iridium-enhanced) spark plugs are the most recent development. They are characterized by very thin central electrodes that are extremely hard and can handle very high temperatures. They last up to four times longer than platinum models. Though they may not be a great deal more expensive, the choice of iridium spark plugs for riding mowers is limited.
Size and Electrode Gap
The length of the portion of the spark plug that appears outside the engine is seldom important, but the diameter and length of thread inside the motor is vital. If the diameter is wrong, it simply won’t fit: It either won’t screw in, or it will be too loose. If the length (also called reach) is wrong, it might still fit but there can be other problems. If it’s too short, the spark won’t be in the right place in the combustion chamber, and the motor won’t run properly, if at all. If it’s too long, there’s a real chance of the piston hitting the spark plug, which can cause serious damage. Due to these facts, it’s vital to check all dimensions.
The electrode gap has an impact on performance. It should be accurately set by the factory when the spark plug is made, but as it wears, it becomes larger. Historically, that gap would be checked during maintenance and a gap tool used to adjust the outer electrode. Vehicle tuners may still do so, but most mower owners simply replace the spark plug with a new one; some spark plugs can’t be adjusted, anyway.
Recent innovations also have seen new designs in the shape of the outer electrode. The aim is to produce a more precise spark which burns the fuel and air mixture more efficiently. Prices remain competitive, and it’s an increasingly popular option with those looking for the best spark plug for their riding mower.
Spark plugs also can be described by their heat range. They are either hot plugs or cold plugs. Typically, engines with modest performance use a hot plug for a better fuel ignition, whereas high performance engines use a cold plug for improved heat dissipation.
It’s another area where the wrong choice can cause problems. There’s a misconception that hotter plugs improve performance. However, if the plug runs too hot, the insulation around the central electrode can melt. At best, this causes irregular firing. At worst, it will break away from the spark plug and damage the piston. Spark plug manufacturers usually have comparison charts for other makers’ products so heat range can be checked, along with the plug’s physical attributes.
The ignition circuits that allow a plug to produce a spark also cause electromagnetic interference (EMI) and radio frequency interference (RFI). These can actually disrupt spark performance. To prevent this, a suppressor is used; it is usually built into the insulation around the central electrode. The intent is to make the mower engine run more smoothly. Though usually present, it’s a feature not often mentioned.
There are manufacturing standards that help support any quality claims that a company may make in spark plug packaging and advertising. Both SAE International (formerly known as the Society of Automotive Engineers) and ISO (the International Organization for Standardization) produce standards for spark plugs, which are extensive and highly technical. Many spark plug manufacturers comply with these requirements and may even state that they are in compliance. It’s important to understand these standards organizations cover the quality and accuracy of manufacturing, not any performance characteristics.
Our Top Picks
Now that you know a little more about the choices in terms of durability and performance, it’s time to look at some of the best spark plugs currently available. None of these are particularly expensive, but the assigned categories provide a quick and easy reference to each type.
American company Champion has more than 100 years experience in spark plug manufacturing, and the Copper Plus models offer reliable performance and value for the money. The Copper Plus 71 Spark Plug has special corrosion-resistant coatings for the body, and the patented RFI and EMI suppression help the engine run more smoothly. Quality is underlined by compliance with both SAE and ISO production standards.
The range of spark plugs is remarkably extensive for riding mowers and lawn tractors, and while many spark plug companies produce a limited range for garden machinery, Champion usually has a suitable replacement, whatever the make and model.
There can be a reluctance to buy low-cost, consumable engine products from overseas. Though prices can seem a bargain, if components don’t have the required quality and durability, then any savings turn out to be a false economy. Fortunately, that’s not the case with the excellent Maxpower spark plugs. Though it’s always important to check specifications, these have been designed specifically for popular riding mowers from brands like John Deere and Husqvarna and also fit many Kohler motors.
It is a basic, no-frills copper spark plug, so it won’t compete with platinum or iridium models in terms of life expectancy. However, it does produce a reliable spark for around half the price of similar “big name” copper alternatives.
The E3 Lawn and Garden Spark Plug is a copper model at its core, but it has a unique outer electrode shape that wraps around the central electrode. This is designed to deliver a more precise spark, therefore increasing fuel consumption while also significantly lowering emissions. It also reduces the buildup of carbon deposits, thus extending durability. The DiamondFIRE technology is so unusual it has been patented.
The E3 spark plug is available to fit a wide variety of four-cycle riding mower and lawn tractor motors, and a two-cycle model also is available. While more expensive than many competitors, this spark plug’s increases in performance and improved fuel efficiency would more than compensate over the lifetime of the spark plug.
Briggs & Stratton motors are fitted to many of the best riding mowers. While spark plugs from several brands can be used as replacements, there are times when the original brand is simply the best spark plug for the job. This high durability, platinum model also can fit a number of other L-head (or flat head) engines, which is a design popular on riding mowers for their compact dimensions.
The increased cost when compared with ordinary copper spark plugs should be balanced against consistent performance throughout an extended service life. This generally results in better fuel economy and, depending on model, ensures compliance with EPA emission regulations.
The Autolite Xtreme Performance brand by Fram uses electrodes made from a combination of iridium and platinum. The benefits are both precise spark production and excellent durability. The tip of the central electrode is only 0.6 millimeter (0.02 inch) across, helping to place the spark in the optimum position within the combustion chamber. It is supported by a patented platinum sidewire that is highly resistant to wear.
There is some debate as to whether comparatively low performance engines, like those fitted to riding mowers, really take full advantage of iridium technology. However, the competitive price of Autolite’s XP spark plugs makes them an affordable choice.
The Advantages of Owning the Best Spark Plugs
Spark plugs, like oil changes, are part of the regular maintenance routine for any engine. However, it’s something that can get overlooked, which is to the detriment of the vehicle. Choosing the best spark plugs for a riding mower and changing them regularly makes good financial sense and offers a number of additional benefits:
- Starting a riding mower will be easier with fresh spark plugs, particularly if the weather is a little cold or damp.
- The engine will run at peak performance throughout its range, which means optimum fuel efficiency.
- The engine will be more responsive to throttle input, which results in a smoother, quieter ride with reduced vibration through the frame and seat.
- The engine will burn more cleanly, reducing sooty deposits and tar, which is good for its long-term durability. It also means lower emissions, which is good for the environment.
FAQs About Spark Plugs
This guide’s detailed look at the technical aspects of the best spark plugs for a riding mower combined with the reviews of some of the top models currently available may have helped provide better understanding of these devices. If you still have lingering questions, the following answers to some of the common questions may help.
Q. Does it matter what kind of spark plugs you use?
There are two ways to look at this question. Yes, the kind of spark plug matters, because the motor depends on a certain size and type for efficient running. However, as long as the size and specification is correct, spark plugs can be used from a manufacturer other than the original equipment manufacturer. If compatible, platinum or iridium alternatives, instead of copper spark plugs, can be used, too.
Q. How often do I need to replace my spark plugs?
The manufacturer will usually provide guidance in the owner’s manual. Replacing spark plugs once a season is usually sufficient for copper models, though others may last longer. It’s difficult to give an accurate estimate because much depends how often you mow, for how long, and how hard the motor has to work.
Q. What are the symptoms of a faulty spark plug?
Difficulty starting or failure to start are symptoms of a faulty spark plug. A misfiring engine or excessive exhaust smoke are all common indicators.