What Are The Best Spark Plugs? (2019 Review Guide)
Your spark plugs are a critical component of your engine. If your spark plugs are malfunctioning, your engine won’t be capable of producing combustion, and your car simply won’t move. If multiple spark plugs have failed, your engine might get flooded with gas.
Given that they are such a fundamental part of your engine, it’s hard to figure out what you need from your spark plugs. The electrical properties of the spark plugs may not be obvious to you, nor is it clear which spark plugs are more durable than others.
In this article, we’ll walk you through our take on some spark plugs so that you will know which ones are winners and which are duds.
- What To Look For In A Set Of Spark Plugs
- Our Spark Plug Reviews
- 1. NGK 5464 BKR5EIX-11 Iridium IX Spark Plug
- 2. NGK 6619 Iridium Spark Plugs LFR6AIX-11
- 3. Denso (4504) PK20TT Platinum TT Spark Plug
- 4. NGK 7090 BKR5EGP G-Power Spark Plug
- 5. Bosch Platinum 2 #4308 Spark Plugs
- How Long Should My Spark Plugs Last?
- How Do I Make My Spark Plugs Last Longer?
- How Many Spark Plugs Do I Need?
- Are All Spark Plugs Compatible With All Cars?
What To Look For In A Set Of Spark Plugs
Spark plugs have some features which you should be on the lookout for. These features are relatively common in isolation, but fairly rare as a set. In fact, some of the best features of spark plugs are contradictory, so you will need to decide to make a tradeoff at some point.
The most important feature of spark plugs is reliable ignition. The details of what constitutes reliable ignition will depend on the kind of fuel you use the most frequently. If you use difficult-to-ignite fuel like biodiesel, it will take a more powerful spark plug to ignite it reliably.
If, on the other hand, you only use high quality fuel, you can make do with a much less aggressive spark plug.
To make ignition possible, the spark plug needs to be powerful enough to pass a spark through the compressed fuel in the engine cylinder. If a spark passes through the compressed fuel with enough resistance, the fuel will ignite.
More than one spark increases the chances of the fuel igniting significantly. The area in between the two sparks is very hot, which means it will immediately ignite. The result is a lower chance of engine stalling due to failure to combust.
More sparks mean that the spark plug needs more electrical energy, however. For most cars, this will not be a noticeable strain on the electrical system. In niche cases, the voltage requirement may be too high. You will need a lower-voltage spark plug in these cases.
Spark plugs with lower voltages tend to be more durable, too. Less stress on the spark plug means that the spark plug will have a longer life and be less likely to fail.
Failed spark plugs cause the engine to flood and combust out of sync. Combusting out of sync can damage the engine, but typically it causes the engine to stall. One failed spark plug can bring your entire car grinding to a halt.
Diagnosing a spark plug failure can be very difficult, too. It’s best to find a durable spark plug that won’t fail.
The final important feature of spark plugs is that they seal the fuel within the engine cylinder. The worst spark plugs have tiny gaps in between the engine cylinder. When the engine compresses the fuel during the down stroke of the cylinder, the fuel is forced through these tiny cracks.
The fuel will then leak out into the other portions of the engine. This can cause serious problems with your engine, and is also an environmental hazard. It’s best to find the spark plugs that don’t have this issue.
Our Spark Plug Reviews
1. NGK 5464 BKR5EIX-11 Iridium IX Spark Plug
The NGK 5464 BKR5EIX-11 Iridium IX Spark Plug is intended for high-performance applications where its high build quality will do the most good.
- Protects against engine seizing
- Protects other components from engine issues
- May disguise problems in the engine by compensating for them
The NGK Iridium IX spark plug has a very stable spark. Because of the precision-cut tip of the spark plug, the spark is consistent, which puts less stress on the engine. You won’t need to worry about a subpar spark damaging your cylinders.
This spark plug has a foul-proof insulator nose which is spined. The advantage of the spined insulator nose is that there are fewer opportunities for gas leakage outward in the event of an overpressure problem caused by another component of the engine.
The result is that this spark plug makes your engine more resistant to seizing. High-performance engines that run on the edge of their limits will be well-served by this spark plug. The plug itself won’t corrode so you will have it for a long period of time.
2. NGK 6619 Iridium Spark Plugs LFR6AIX-11
The NGK 6619 Iridium Spark Plugs LFR6AIX-11 is another spark plug offering from NGK which is optimized for heavy-duty use.
- Helps with pre-ignition
- Seals combustion content into the cylinder
- Broadly compatible
- Difficult to install
Like other NGK spark plugs, these plugs are engineered for maximum quality. You’ll get a great warranty which shows the company believes in these plugs. Likewise, you will avoid problems with your engine seizing.
Your engine will not stall as frequently if it is in subpar conditions. You will be able to avoid difficulty with fuel flooding problems and also problems with pre-combustion.
In instances where your engine is pre-igniting, these spark plugs may be part of the solution owing to their sealant and ribbed surfaces.
3. Denso (4504) PK20TT Platinum TT Spark Plug
The Denso (4504) PK20TT Platinum TT Spark Plug is unique and powerful because of its twin-tipped technology.
- Ultra-high heat resistant design
- Double sparks for better fuel ignition
- Great for biodiesel
- Doesn’t do everything it claims to do
Most spark plugs only have one tip where the spark ignites the engine at the electrode. This spark plug has a single electrode, but, thanks to voltage differentials within the metal, produces two sparks from the same electrode.
The utility of this feature may not be immediately obvious. One spark is enough to ignite the fuel in most situations, right? The advantage of having the second spark is the fuels which are more difficult to ignite — like biofuels — will have a much easier time combusting.
Especially if you plan on using a lot of these difficult-to-ignite fuels, this spark plug can be a huge boon to your engine. It’s possible that this spark plug could make the difference between your engine running and it seizing or flooding.
For normal types of fuel, the dual-spark functionality doesn’t contribute much. Nonetheless, the spark plug boasts improved fuel economy and faster start times owing to its platinum and titanium build.
While it’s true that the metals of the plug make it extremely durable and lightweight, there is not a high chance that the spark plug will increase fuel economy. So, while this spark plug is great, the marketing is not accurate.
4. NGK 7090 BKR5EGP G-Power Spark Plug
The NGK 7090 BKR5EGP G-Power Spark Plug uses a unique low-voltage ignition design which helps to prevent pre-ignition and ensures that your car has more electrical power to use elsewhere.
- Low-voltage design saves power
- May improve fuel economy
- May be easier to start with low battery power
- May struggle to ignite dilute fuels
Many spark plugs advertise that they are high-voltage. The appeal of a high-voltage spark plug seems obvious — more voltage equals more ignition, right? Not necessarily. This spark plug uses a low-voltage sparking design which is far more energy efficient than other designs.
This spark plug will ignite fuel as effectively as other plugs. Importantly, it won’t take as much energy from your battery to start the car. While difficult to measure directly, it is entirely possible that using these spark plugs will allow your car to start in situations where the battery is drained, unlike other spark plugs with a higher energy requirement.
The other advantage of low-voltage spark plugs is that your engine won’t need to work any additional amount to provide additional electrical energy. You may find that your fuel economy improves as a result.
5. Bosch Platinum 2 #4308 Spark Plugs
The Bosch Platinum 2 #4308 Spark Plugs are an extremely durable set of spark plugs which will almost certainly outlive your car’s lifetime.
- Very durable
- Multiple spark paths
- Redundant ground electrodes
- Less effective than other double air-gapped electrodes due to the durable design
Most spark plugs are fairly durable, but their electrodes tend to fail over a long enough period. The Bosch spark plugs buck this trend definitively. These spark plugs are normal in appearance but are ultra-durable.
The way the Bosch spark plugs accomplish improved durability at the same time as good ignitability. The spark plugs have multiple spark paths which occur via a central electrode and two ground electrodes. This means that the spark traverses through the “air” of the engine to ignite the fuel.
While air-gap firing is a common feature in the spark plugs of today, most air-gap firing electrodes suffer a minor hit to their durability compared to no-gap plugs. The way the air-gap is built into the plugs tends to leave a thin piece of metal consistently exposed to the stressed of the engine.
This is not the case with the Bosch spark plugs. These plugs use air-gap firing at two points without any vulnerable pieces, so they offer superior ignitability alongside superior durability.
How Long Should My Spark Plugs Last?
The best spark plugs last 20 years with strenuous usage. The worst spark plugs might last as little as a year. The best indicator that you have is the length of the manufacturer’s warranty.
The longer the warranty, the more confident that you can be in your spark plugs lasting for the long haul.
How Do I Make My Spark Plugs Last Longer?
Using the right kind of fuel for your car and your engine is the best way to make your spark plugs last a long time. The main issue is the viscosity and ignitability of the fuel you are using.
The more efficiently your spark plugs ignite the fuel, the longer they will last. If there is excess fuel after combustion, it may put additional stress onto the spark plugs.
How Many Spark Plugs Do I Need?
Your car needs one spark plug per cylinder of the engine. The spark plug sits at the bottom of the cylinder, where it then ignites the fuel. So if your engine’s cylinders aren’t each equipped with a spark plug, the fuel there will not ignite and the engine will stall or flood.
If you aren’t sure how many cylinders there are in your engine, you can easily figure it out. Many standard cars have a six cylinder engine, which means that you will need six spark plugs. Performance vehicles will have either eight or twelve cylinders.
You may need to pick spark plugs that are better suited to a higher performance engine in these cases, however.
No matter how many spark plugs your car requires, you must always use the same spark plugs in every cylinder. That means when you replace one spark plug, you should replace them all. Likewise, do not mix and match spark plugs of different brands.
This will cause your engine to stall and potentially be damaged.
Are All Spark Plugs Compatible With All Cars?
No, you will need to find the correct set of spark plugs for your car. The diameter of spark plugs is standardized, but the protective ring at the bottom of the spark plug varies considerably.
If you pick a spark plug that is too loose, the fuel will leak into the rest of the engine and cause problems. If you pick one that is too tight, there may be additional stress on your engine cylinders if it fits enough to stay seated whatsoever.
The best guidance for your spark plug compatibility is the manufacturer’s guide. Most manufacturer’s guides will have a comprehensive list of car models and engine models that are compatible. You should also check reviews online to make sure there aren’t any other issues.