The humble spark plug. Whilst it may seem like one of the simpler components of your engine it is also one of the most important. After all, the internal combustion engine simply cannot operate without a spark plug.
So no spark plugs, no engine. No engine, no car. Over 140 years of technological innovation wiped out – without the spark plug, we have to ask the Amish to teach us all how to drive horse and buggies again.
They can also make a big difference in the driving experience and smooth operation of your car, so choosing the right plugs to either upgrade or replace your existing set is vitally important. How do you know which plugs are the best for your engine set up? Well, the first thing you can do is read this guide…
Best Rated Spark Plugs in 2019:
We’ll start with one of the more premium products on this list – it is in fact the most expensive. However, it is also a multipack, which is something of a rarity these days, when many manufacturers look to sell plugs individually.
So whilst you are shelling out the most bucks to buy this product compared to some others, you are getting a pack of 6. So if you need to replace multiple plugs in one go this could actually be the economy option. Plus, it’s not like these things rot – if you don’t use them all, just tuck them away for the future.
They are well worth saving too, as they are a decent all round plug. Iridium is a premium spark plug material, often giving around 25% longer life span compared to cheaper platinum models. The super fine electrode wire also helps to make this a very efficient model.
- Weight11.5 oz
Fine Wire Electrode
Pack of 6
Whilst iridium is overall the best material to look for in a spark plug, it’s also pretty expensive. Platinum constructed plugs are not a million away in terms of quality and life span, and this model from DENSO is one of the better options on the market right now.
It employs a dual platinum construction, with a platinum disk and platinum electrode tip. The electrode itself has a width of 11mm which is a little thicker than you will find on truly premium plugs however it’s not going to have a noticeable effect on performance in a normal car in regular driving conditions.
Purified Alumina Powder is used as an insulator material too, which increases thermal conductivity and should help provide a long working life span. This item packs in quite a lot of features into a relatively small price tag. Well done, DENSO.
Platinum Twin Tips
- Weight0.32 oz
Purified Alumina Powder Insulator
This plug from NKG, quite like the one we discussed above, also uses an innovative design to try to supply the performance of iridium-constructed models at a cheaper price.
Whilst the previous model utilized a double platinum construction, these plugs only have Platinum on the electrode tip. However, they make up with that by employing an incredibly thin (0.6mm!), laser welded tip. That thinness of the electrode will lower the power needs without affecting performance, leading to fast engine starts and improved efficiency.
As a four pack the initial purchase price is of course higher than a single plug, however divide the price by 4 and the individual price for each one is about the average price for a decent product.
Alloy Spark Plug
Thin Electrode Tip
- Weight1 lb
0.6m Electrode Tip
4 Pack of Plugs
Platinum on tip only
The German firm Bosch are a premier manufacturer of electrical goods (they make my kettle & my refrigerator for example) so first of all you know you are getting a quality product – the name is the guarantee.
What we have here is a very innovative design. The plug tip has been re-designed from the ground up, producing a product that looks very different from the traditional model. What we have here are four yttrium-enhanced electrodes instead of the single electrode & cap system seen on traditional plugs.
This provides a plug that delivers excellent performance without having to rely on expensive materials like iridium or platinum. The design is also very straightforward to use – it is literally a plug and play model, no adjustments required after install.
This is a great product that will not cost you as much as you might assume. Gut gemacht, Bosch.
4x Yttrium Enhanced Ground Electrodes
Low Maintenance Design
- Weight0.32 oz
Electrodes deliver powerful sparks
Easy to Install – No Adjustments Required
Relatively Expensive (not that expensive though)
This is a high performance plug with a number of unique features. The first to note is that lovely, 0.6mm width on the tip. Again, that thin tip is going to really enhance engine performance. Add in the fact it’s laser welded platinum and that’s a very good start.
The unique insulator noses are specially designed to improve throttle response too. So this is overall a pretty high spec plug for a relatively low price tag. Therefore, if engine performance is the most important factor to you – but you don’t want to take out a new credit card to buy your plugs – you should definitely take a look at these.
Unique Design Insulator Noses
- Weight1.92 oz
Say hello to the second most expensive product on this list. It is more than 3 times the price of some of the other plugs here so you better be getting a heck of a good plug for that outlay, right?
Well Denso don’t disappoint. This is a premium price tag admittedly, but it is for a premium product. Not only does it come with Iridium tips in its construction, it also has an incredible 0.4mm width electrode.
Now, as we’ve stressed already – iridium is the best sparkplug material. The thinner the electrode, the better the performance. So in this product we see both the best materials being used and also the thinnest electrode on the list.
That explains the incredible engine performance this product can bring – but it also explains the high price.
- Weight5.6 oz
High Quality, Laser Construction
Super High Performance
From the most expensive product on the list to the cheapest – but please don’t write it off and scroll straight past!
True, there is nothing particularly innovative about this plug. Couple that with the copper construction on the electrode and this is a very basic model. However, it is also a nicely put together plug with built in anti corrosion resistance. It is a strong, dependable plug that is built to a high standard for a long working life.
Some engines, especially older ones, specify a copper plug. If your engine spec sheet calls for copper, this is an excellent option for a very reasonable price.
Built in Corrosion Resistance
Solid and Dependable Design
- Weight0.8 oz
Great for Older Model Cars
Would you like to peek behind the curtain of the writing process? I made a mistake in this list when I was drafting it. I referred to a different plug as the most expensive, because I saw the price and assumed no spark plug could possibly cost more.
Then I saw this product, our second entry from Bosch.
The price of this product is eye watering – but my God are you getting a top, top quality spark plug here. That name on the carton is your first guarantee of quality. Second comes from the materials – Iridium electrode and an Iridium cap. That this plug utilizes so much iridium explains both the cost and the incredible high performance.
It also brings long life – around 4x times the life span of a standard copper plug. Bosch are in fact so confident in the high performance and long life span of this plug, they will give you a 7 year performance satisfaction guarantee.
7 Year. Guarantee. 7!
Yes, this is expensive. But look at it as a long-term investment, divide the price by the years of service you’ll get, and this plug basically buys itself.
Double Iridium Design
7-Year Performance Guarantee
- Weight0.8 oz
Incredibly high performance
Long life span
Twice the Iridium for Twice the Fun!
Expensive (very expensive!)
These products are specially designed for high performance vehicles and have a number of features to achieve that aim. The first is the use of iridium, which by now you should know is the best material for high performance. They also have a nice, thin 0.6mm electrode, again aimed at increasing engine power and performance.
Finally, it has a pretty unique feature, a set of corrugated ribs on the insulator. They help to prevent flashover and in conjunction with a triple gasket seal eliminate any leakage of the gas mixture used for combustion in the engine. That helps to extract every ounce of power from your engine.
They are not cheap, and may be a bit too performance engineered to warrant the extra money if they are going in a normal car for every day driving. But if you really care about exacting the maximum power and performance from your engine they could be an excellent investment.
Designed for High Performance
- Weight1.6 oz
Great for High Performance Engines
Overkill for a Regular Vehicle
Basically the exact opposite of the plug above, this product from Autolite is not really designed with premium performance in mind.
What we have instead is a superb everyday plug that is perfectly suited to go into a normal car and perform well in normal, everyday situations. So if you use your car to do doughnuts and hand break turns in parking lots and out run the cops on the freeway – this isn’t the plug for you!
If you commute to work, drive to the mall – in other words use a normal car to do normal things – this is a great plug made with very good materials to a tried and trusted design. It’s a great middle ground between cheaper products of inferior manufacture and materials and the top end, premium plugs and their high prices.
To put it simply – It’s not going to perform miracles, but it’s not going to let you down either.
- Weight6.4 oz
Excellent, Everyday Plug
Tried and Tested Design
No Stand Out Features or Materials
Best Spark Plug Buying Guide & FAQ
There is our list of the best park plugs out on the market today. As we mentioned up top, these deceptively simple products are in fact very important to the smooth running of your engine, and when they start to fail can reduce fuel efficiency by up to 30%.
So choosing the correct plugs is very important. To chose the right ones you need to understand how they work, how to work on them and how to spot the signs of the spark plug is perfect for your needs.
How Spark Plugs Work
Well this seems as good a place as any to start – how do Spark Plugs work? Well sir, you just plug them in and they spark. Simple.
Ok, they are a little more complex.
A spark plug is first and foremost an electrical device. It plugs into the cylinder head of a typical engine (*). The cylinder head is flooded with a mixture of air and fuel (gasoline) that the spark plug ignites. This tiny explosion (and that is really what it is!) drives a piston that is attached to a crankshaft that transfers the energy (via a couple more connections) to the wheels of your car, propelling the vehicle.
That’s it! Or at least that is the absolute basic description of the workings of the internal combustion engine. But you should be able to see how important the spark plug is, right?
No spark, no combustion – no engine.
*Diesel engines are a little different, and don’t use spark plugs. Instead, they use Glow Plugs. So if you have a diesel car and have read this guide all the way to this point then… sorry.
Different Types of Spark Plugs
Even though they are relatively simple little things there are a few differences in the various models that you will see available.
Broadly speaking, they are all of the same design – with the exception of the first Bosch plug in the list above, which instead of the typical electrode and cap arrangement had a special 4-point electrode construction. But that was 1 plug from 10 that was a totally different design.
Instead, the main area where you will notice differences is in the materials used for the electrode and sometimes the cap, which will be constructed with one of three materials:
- Copper – The original, but sadly not the best! Copper spark plugs are the most basic on the market, and as such are the cheapest. However, the have been largely replaced in modern cars by plugs made of Platinum or Iridium. These two materials just have such better performance and lifespan, many modern engines simply can’t run with copper plugs installed. On the other hand, older engines can often run better with copper, so there is still a place for them.
- Platinum – A great middle ground material, platinum provides a real boost in performance and fuel efficiency compared to copper, but without the premium price tag of iridium plugs. For a real performance boost, look for plugs that use double platinum – both in the electrode and in the cap.
- Iridium – The pinnacle of spark plug tech. Iridium plugs will deliver the best performance, the best fuel efficiency and the longest life span – but also the highest price tags.
Signs That you Need to Change your Spark Plugs
Spark plugs don’t last forever. The typical copper ones will wear out between 10,000 to 20,000 miles. Platinum will get you to around 50,000 to 60,000 and iridium even further – some types can survive up to 100,000 miles.
You don’t want to wait until the plugs are completely worn out however as that will affect engine performance and fuel efficiency – costing you way more money than what a new set of plugs will set you back.
Look out for these signs that your plugs are on the way out, and change them nice and early:
Difficulty Starting the Engine – The biggest give way that the plugs are tired out is if the car struggles to start, especially in the morning.
Rough Idling – We all know what a car’s engine should sound like when it idles, right? It should be a nice smooth and consistent sound – almost a purr. If it is too loud or irregular sounding then the plugs could be the fault.
Misfires – Poorly plugs won’t help the cylinder fire properly, leading to – you guessed it – misfires.
Poor Acceleration – If you put your boot down at a green light and the car moves away like an asthmatic sloth then plugs could be the problem.
Poor Fuel Efficiency – An engine running on old, worn out plugs will simply not be running as efficiently as it could. If you notice that you’re getting less mileage from each tank of gas, it could be time for a fresh set of plugs.
When Are Cold or Hot Spark Plugs Best?
This is a case of opposites attracting. Spark plugs can be designed to have different temperature tips – cold plugs have colder tips and hot plugs have even colder tips. No, wait – hot plugs have hot tips.
When picking the right one, just think opposites. Cold tips are better to use on a very, very hot day. They are also best for high performance engines and/or engines with high RPM. That’s because the tips car cooler, so they operate at a lower temperature allowing the plug to remove excess heat form the engine more efficiently.
Hot plugs are, unsurprisingly, the exact opposite. They are designed to operate with hot tips that means they are always toasty warm even when the air being brought into the engine is cold. This is important, as if the plug is operating in an environment that is too cool, the combustion in the cylinder head won’t be as efficient as it could be. That in turn affects engine performance, and can also lead to deposits building up on the plugs, which shorten their life span.
At the end of the day though you probably don’t need to worry about this too much. The exception would if you are very concerned about getting the maximum engine performance possible, or if you live somewhere very cold (Alaska) or very hot (Florida). In those instances, it could improve engine performance and prolong spark plug life span to select the correct temperature plug.
For most of us though, the types of plugs recommended for our vehicles will take into account the correct temperature, so don’t worry about it too much.
How to Change & Inspect Spark Plugs
Removing spark plugs is relatively straight forward, and this guide should provide everything you need.
Once you’ve got the plugs out, you can tell their condition by how they look, so for example:
- Look Fine – If they look fine, and the engine is running perfectly, then the plugs are ok to put back into the engine.
- Fine, with red coating – The engine works fine, the plugs look ok but with a bit of a red coating. That is just leftover additives from cheap gasoline. Clean them off with a cloth and put them back.
- Worn – If the plug electrode looks worn, i.e. thinner or more brittle than a new plug, it’s time to replace it.
Basically, if the electrode looks ok, the plug is probably ok, because that thin little wire is really the working part of the plug and takes the most punishment.