The Ultimate Spark Plugs Buying Guide


A Guide To Buy Spark Plugs

Have a full tank but still stranded or maybe you are experiencing rough idles and bad fuel economy? All these and many other issues can be found due to blown spark plugs. Although spark plugs are tiny components in even the largest engines, their role in gasoline engines is vital and irreplaceable. Use this guide to find spark plugs best suited for your vehicle and get efficient and reliable performance.

Our Top Picks For Spark Plugs

Table Of Contents

1. What Is The Function Of Spark Plugs?


In a gasoline engine, there are three basic elements essential for the production of power or for the engine to operate: air, fuel and spark. The supply of air is done through the intake manifold and fuel is delivered using the fuel injection system. The spark is provided by the ignition system and consists mainly of the spark plug and the ignition coil. The spark plug has two electrodes separated by an air gap and as a high voltage current passes through one electrode, it jumps the gap to reaches the other electrode. This jump creates a spark essential for igniting fuel-air mixture in the engine’s combustion chamber. 

The voltage is produced by the ignition coil which is essentially a step-up transformer that converts the battery’s 12v to more than 20,000 volts necessary to create a spark strong enough to ignite the fuel-air mixture.

The job of a spark plug is to ignite the fuel-air mix present in the combustion chamber to create power. It also helps dissipate some of the engine heat by absorbing it through the shell. If the spark plug fails or works improperly, the entire engine operation is compromised. Engine misfiring, inability to start and reduced acceleration are few common results of spark plug failure. 

2. What Are The Types Of Spark Plugs?

Spark plugs can be classified based on the material used in their construction, operating temperatures and design.

2.1. According To Materials

2.1. According To Materials


Spark plugs can mainly vary based on the materials used in their construction and the resulting types of spark plugs are as follows:


A. Copper Spark Plugs

Copper is a very good electrical and heat conductor, which are ideal requirements for spark plugs. Copper spark plugs have been used since the very beginning and are still used as original equipment on many vehicles due to their affordable manufacturing and material costs. Most spark plugs have a solid copper core and older copper spark plugs were completely made of copper including the centre and side electrodes. But since copper has a low melting point, these were highly susceptible to rapid wear due to the softer material. Modern copper plugs have a nickel alloy centre and nickel-plated side electrodes that are more wear-resistant and therefore give the plugs a longer service life. 


B. Platinum Spark Plugs

Platinum material is harder than copper and nickel providing better erosion resistance and hence longer service life. Platinum spark plugs also run hotter which helps burn the deposits on the spark plug and helps reduce the risk of fouling and extends the spark plug life. 

There are two types of platinum plugs: Single and Double Platinum spark plugs. The single platinum plug is essentially a copper-nickel plug but with a platinum disc on the centre electrode. Since platinum is sturdier than nickel, the sharp edge of the platinum centre disc lasts longer. Double platinum plugs have platinum discs on the side electrodes as well giving the plug even better wear resistance and lifespan. Most modern vehicles come factory equipped with platinum plugs due to their efficiency, performance and longevity. 


C. Iridium Spark Plugs

Iridium is much stronger and harder than platinum and also has a higher melting point which when applied to spark plugs, yields an exceptionally sturdy plug that is efficient at heat retention, highly wear-resistant and provides better performance. The increased strength and hardness of Iridium allows the plugs to last up to 25% longer than comparable platinum spark plugs. Iridium spark plugs have a narrower center electrode which is made of fine wire. This helps increase the firing efficiency. Due to the many advantages of iridium spark plugs, these are the ideal choice of plug for most modern vehicles. The increased benefits and superior material choice is why iridium spark plugs are more expensive than other types. 

2.2. According To Operating Temperature

A. Hot Or Cold Spark Plugs

The heat range of the spark plug is derived based on its heat dissipation properties. To get varied heat ranges, the internal length of the core nose is altered. This nose is covered with an insulator material. By decreasing the length of the nose, the insulation material also decreases which allows the faster heat transfer from the tip to the engine head and in turn keeps the spark plug cold. This is called a cold spark plug. Alternatively, by increasing nose length, the insulation material increases and heat transfer is restricted which causes the plug to stay hotter. This is called a hot spark plug. Both types of plugs are used in different engine applications. 

2.3. According To Design

2.3. According To Design


The spark plug design can vary based on the number of ground electrodes it has and the level of the centre electrode projection. The most common type of spark plug has a simple ground or side electrode, but certain ignition systems like wasted spark DIS use plugs with up to four ground electrodes. The projection of the central electrode can determine the effectiveness of the spark plug. 

3. What Should I Look For When Buying Spark Plugs?

Spark plugs are critical engine components without which the functionality of the vehicle is compromised. How many times have you struggled to start your vehicle just because one or more spark plugs were dead? Ensuring your find the right spark plug for your vehicle is important for reliable engine performance.

3.1. Material

As discussed earlier there are a few different types of spark plugs based on the material used in their construction. Not every vehicle can operate on every type of plug so you need to find the one for your vehicle. Start by checking the owner’s manual for manufacturer-recommended types. In most cases, you need to stick to the manufacturer’s recommendation for optimal engine operation. 

If the owner’s manual states to use copper plugs then you cannot upgrade to platinum or iridium because these plugs are meant for high-tension ignition systems whereas copper works well with distributor-type ignition systems common to older models. But platinum spark plugs are recommended then you can upgrade to an iridium spark plug. Vehicles that come with double platinum spark plug cannot use single platinum or copper plugs. However, you can upgrade to iridium-platinum spark plugs or double iridium spark plugs which have iridium on the centre electrode and either platinum or iridium on the side electrode making it suitable for wasted spark DIS (an ignition system that creates a spark from side to centre electrode as the partner cylinder goes in compression stroke). 

3.2. Heat Range - Hot Or Cold Spark Plugs

3.2. Heat Range - Hot Or Cold Spark Plugs


Deciding on which type of plug to use depends on the type of vehicle you drive. For performance vehicles with high horsepower numbers, you need to opt for cold spark plugs so as to maintain the optimal spark plug operating temperature. But for most normal vehicles and light-duty applications, hot spark plugs are sufficient. This is because, for normal engines, the engine operating temperatures do not go extremely high which means the spark plugs needs to reach operating temperature quicker for proper functioning. Whereas in performance engines, the operating temperatures are very high which can cause the spark plugs to overheat without sufficient heat dissipation. This is why cold spark plugs are best for high-performance engines. 

3.3. SIze

3.3. SIze


The size of the spark plug hex or nut size determines the plug for installation. While most vehicles use the same spark plug size, exceptions do exist. The most common spark plug sizes are 5/8" or 16mm and 13/16” or 20.5 mm. You can refer to your owner’s manual for the right spark plug size for your vehicle to ensure a perfect fit and therefore function. 

3.4. Gap Style

3.4. Gap Style


The space between the ground and centre electrode is called the spark plug gap and is an important factor when choosing a spark plug. Different engines require different spark gaps for the best performance. Refer to the owner’s manual to learn about the ideal gap range for the spark plug used in your engine. If buying spark plugs that cannot be gapped then make sure it is a perfect fit for your can. Most spark plugs can be gapped and you can measure the space accurately using a gap gauge. Spark plugs for cars generally gap between 0.6mm and 1.8mm (0.024 and 0.071 inches).

4. Top Spark Plugs Brands I Should Choose From?

4.1. NGK Spark Plugs

4.1. NGK Spark Plugs


NGK Spark Plugs offers a wide variety of products for various automotive and industrial applications. They are committed to providing world leading Japanese technology of spark plugs, glow plugs and sensors for better performance for customer vehicles. Every day they make the greatest conceivable efforts to meet the product expectations and requirements of their OEM & aftermarket customers. Keeping this in consideration, NGK focuses on quality & services more than anything else and delivers nothing but the best.



A. NGK Iridium Spark Plugs

Laser Iridium® spark plugs provide superior ignitability and long service life.  Smallest tip diameter available Iridium / Platinum surfaces ensure slow wear rate providing stable idle, superior anti fouling, improved fuel efficiency and lower emissions



Part Numbers (Stock Numbers): 6509, 93175, 7164, 5464, 7397, 6418, 91187, 3764, 2314, 92873, 93911 and more.


Features:

  • Laser welded Iridium center electrode tip
  • Platinum disc welded to backside of ground electrode provides long life
  • Trivalent Metal Plating for superior anti-corrosion and anti-seizing
  • Faster starts and quicker acceleration
  • Better fuel economy and lower emissions
  • Best OEM Iridium spark plug available
  • Original Equipment Manufacturer approved design


B. NGK Platinum Spark Plugs

Laser Platinum® spark plugs provide high ignitability and longer service life. Dual platinum surfaces ensure slow wear rate providing stable idle, superior anti fouling, improved fuel efficiency and lower emissions.


Part Numbers (Stock Numbers):  3186, 3403, 5018, 3381, 5017, 92213, 1483, 5141, 7096, 90804


Features:

  • Laser welded Platinum center electrode tip
  • Platinum disc welded to backside of ground electrode provides long life
  • Trivalent Metal Plating provides superior anti-corrosion and anti-seizing properties
  • Faster starts and quicker acceleration
  • Better fuel economy and lower emissions
  • Best Platinum spark plug available
  • Original Equipment Manufacturer approved design


C. NGK Standard Spark Plugs

The workhorse, at the heart of smooth-running engines around the world.


Part Numbers (Stock Numbers)6945, 7131, 2771, 7938, 2382, 95839, 3951, 94122, 6987, 96457, 97292.


Features:

  • OEM Quality
  • Triple-Gasket Sealing Process
  • Consistent Performance
  • Plug of Choice in Millions of Vehicles
  • It is designed to meet or exceed oe replacement
  • OEM quality standards
  • The best quality with affordable price
  • Manufactured to meet exact requirements
  • Fast and smooth installation


For more products, you can visit our NGK Spark Plug section.

4.2. Bosch Spark Plugs

4.2. Bosch Spark Plugs


Bosch develops and manufactures spark plugs in close cooperation with leading vehicle manufacturers. In doing so, Bosch is able to call on its more than 111 years' experience in the industry, and its unique cross-system expertise in automotive technology. Bosch spark plugs are impressive thanks to their outstanding quality and reliability. They not only fulfill the specific requirements of car manufacturers, but are also the perfect choice as aftermarket replacements.


A. Bosch Copper Nickel Spark Plugs

Copper with Nickel Spark Plugs Bosch copper core spark plugs feature a heavy-duty nickel center electrode for longer lasting service life compared to standard copper plugs.


Part Numbers: 7980, 7971, FR7HE02, 8100, FR7NPP332, 9698, 8114, FR8TE2, FR7KPP332, FR8TI332 and more


Features:

  • Meets or exceeds OEM specification
  • Excellent mechanical stability and corrosion protection
  • Direct fit application
  • Lower fuel consumption and reduced exhaust emissions for your vehicle
  • Ensures reliable voltage for smooth engine performance
  • Backed by Bosch Limited Lifetime Warranty


B. Bosch Platinum Spark Plugs


Part Numbers: 6707, 6703, 6715, 6734, 6724, 6721, 6732, 6725, 6743, 6712


Features:

  • Bosch Platinum Spark Plugs are engineered for up to 2X longer service life.
  • Specially engineered Yttrium enhanced ground electrode provides 2X longer service life*
  • Fine wire Platinum firing pin for better ignitability
  • Unique 360 continuous laser weld fuses corrosion-resistant Platinum firing pin to base


C. Bosch Double Platinum Spark Plugs


Part Numbers: 8100, 8110, 8122, 8112, 8118, 8104, 8171, 8117, 8160


Features:

  • Bosch Double Platinum Spark Plugs are engineered for up to 3X longer service life.
  • Laser welded Platinum inlay ground electrode provides 3X longer service life*
  • Fine wire Platinum firing pin for better ignitability
  • Unique 360 continuous laser weld fuses corrosion resistant Platinum firing pin to base


D. Bosch Iridium Spark Plugs

Bosch Iridium Spark Plugs are engineered to deliver both high performance and long life, representing advanced OE spark plug technology. The ultra-fine wire iridium center electrode pin delivers best performance. Unlock the performance in your engine with Bosch Iridium Spark Plugs.


Part Numbers: 9654, 9698, 9608, 9609, 96322, 9601, 9652, 9657, 96300, 9661


Features:

  • Bosch original equipment design, materials and processes represent advanced OE technology
  • Iridium center electrode tip
  • Pre-gapped - no need to gap, providing faster installation.

For more products, you can visit our Bosch Spark Plug section.

4.3. Denso Spark Plugs

4.3. Denso Spark Plugs


The DENSO brand is built on delivering Quality, Reliability, and Value. Whether supplying the world's automakers with reliable OE parts, or developing aftermarket replacement parts at or above spec, DENSO's line of products are built to deliver superior all-around performance every day. 


A. Denso Resistor And Iridium Spark Plug


Denso Iridium Plug Part Numbers (Stock Numbers): 4701, 5303, 5090, 3134, 3253, 3246, 5077, 3301, 3306, 3239, 3174 and more


Denso Resistor Plug Part Numbers (Stock Numbers): 3037, 3381, 5013, 3145, 3178, 3057, 3132, 3119, 3129,3139 and more.


Features:

  • Built-in, Highly Reliable Resistor: All IRIDIUM POWER plugs include a highly reliable, 5,000 ohm monolithic resistor specification to reduce electromagnetic noise that may affect electronic devices. (For all plug types)
  • Highly Corrosion Resistant, Burnished Nickel Plating: The plug housing is plated with burnished nickel, the same as plugs used for racing. It is highly resistant to corrosion and rust even while touring in continually rainy weather and during motocross events. (Low-heat range types excluded)
  • 360° Laser Welding: The process used to mount the iridium tip is a highly reliable “All-around Laser Welding” process that is able to withstand all kinds of driving conditions. (For all plug types)
  • Projected Center Electrode: In order to improve ignitability, the center electrode protrudes more than with conventional type plugs. This improves both acceleration response time and performance.(Only with: IU31, IUH24, IUH27, IX22, IX24, IX27, IUF22, IUF24, IWF22, IWF24, IWF27, IW24, IW27, IW29, IW31, and IW34)
  • 0.4 mm Diameter Ultra-fine Iridium Center Electrode: Using a new iridium alloy with a very high melting point, the tip of the electrode can be made very fine. This enables the reduction of voltage necessary to cause the spark, and greatly improves ignitability. Moreover, the special iridium alloy used was developed by DENSO
  • Taper-cut Ground Electrode: The tip of the ground electrode is cut to a fine taper to reduce the adverse effects of quenching, which greatly improves fuel ignitability. Also, because of the streamlined, taper-cut shape, the fuel-air mixture spreads more evenly in the gap, resulting in steady, reliable igniting of combustion.(excluding IUF27A, IUF31A, IU24A, IU27A, IU31A, IY24, IY27 & IY31)
  • U-Groove Ground Electrode: The U-shaped groove on the ground electrode ensures that the inside surface area is large enough to generate the flame kernel. This shape enables lower voltage needed to cause the spark and results in excellent ignitability without increasing the size of the spark gap. (excluding IUF27A, IUF31A, IU24A and IU31A)
  • Insulator Projection: The projection of the insulator is optimally designed based on each plug's thermal value. This corresponds to requirements unique to thermal value, such as self-cleaning ability at lower thermal values, and heat resistance at higher thermal values. (For all plug types)

Benefits:

  • Vastly improved combustion: Iridium Power has a low required voltage and a high ignitability, resulting in less misfiring and always a spark which dramatically improves combustion.
  • The most advanced technology in the world has been employed to enable use of electrodes, at 0.4 mm in diameter, in the IRIDIUM TT.
  • The smaller the electrode the more concentrated the electric potential at the tip of the electrode and the stronger the electric field that affects required voltage and the lower the required voltage. As a result, combustion is good for all types of -driving, the engine starts easily, and acceleration improves.
  • The above shows the strength of the electrical field in case certain voltage changes on Iridium plug and IRIDIUM TT.
  • The more electrical field strength is getting high, the more it becomes easy to fire with low voltage.


B. Denso Platinum And Double Platinum Spark Plug

  • Twin-Tip Design Proves Two Tips are Better Than One! The Platinum TT® concept originated from DENSO's latest original equipment spark plug technology, the Super Ignition Plug (SIP). Until recently, this OE iridium Twin-Tip design could only be found in the most technologically advanced automobiles. But now DENSO is offering this cutting-edge technology in a brand new platinum/titanium design customized for today's value-minded automotive enthusiasts.
  • DENSO pioneered the use of platinum in spark plug manufacturing. To maximize the longevity and enhance the durability of the spark plug, DENSO applied platinum to both the center and ground electrodes. Platinum offers superior resistance to erosion and corrosion enabling DENSO to create a spark plug capable of consistent performance.


Denso Double Platinum Plug Part Numbers (Stock Numbers): 3264, 3247, 3293, 3253, 3142, 5068, 5077, 3289, 3301, 3302, 3306, 3117


Denso Platinum Plug Part Numbers (Stock Numbers): 4511, 4503, 4512, 4504, 4505, 4506, 4509, 4501, 4502, 4508


Features:

  • 360° Laser Weld
  • Platinum Center Electrode
  • Titanium-Enhanced Tip
  • 1.1mm platinum center electrode
  • Titanium-enhanced alloy ground electrode
  • Minimum-quench electrode design

Benefits:

  • Improved fuel economy
  • Faster starts
  • Enhanced flame propagation for increased engine efficiency
  • Free standing firing pad reduces quenching to generate a more powerful spark

For more products, you can visit our Denso Spark Plug section.

4.4. Champion Spark Plugs

4.4. Champion Spark Plugs


As a world leader in spark plug manufacturing, Champion® knows what it takes to keep your engine running at its best. When it’s time to replace your plugs, Champion® your engine with spark plugs that help improve performance and reduce wear and tear.


A. Champion Copper Plus® Spark Plugs


Part Numbers: 844, 841, 841S, 302, 306, 801, 844S, 91, 328, 587 more.


Features:

  • Copper-core center electrode
  • Patented Ultraseal™ coated shell for maximum corrosion resistance
  • Patented SAC-9 semiconductor resistor.


B. Champion Platinum Power Spark Plugs

Platinum Power spark plugs are a winning combination of their platinum technology with their nickel alloy center electrode, V-trimmed ground electrode and exclusive Heat-active™ Alloy. Together, they offer the durability and performance you can expect from Champion®


Part Numbers: 3570, 3344, 3318, 3034, 3071, 3017, 3405, 3408, 3346, 3066


Features:

  • Platinum center electrode for long life
  • Fine-wire center electrode for greater ignitability
  • V-trimmed ground electrode promotes sharper spark focus


C. Champion Double Platinum Spark Plugs

For faster, stronger, and more powerful performance, choose Double Platinum Power spark plugs. 


Part Numbers: 7440, 7989, 7570, 7034, 7070, 7546, 7983, 7032, 7545, 7340


Features:

  • Platinum center and ground electrode for greater wear resistance 
  • Heat-active alloy maintains stable operating temperature under all engine loads
  • Fine-wire center electrode for greater excitability
  • V-trimmed ground electrode promotes sharper spark focus"


D. Champion Iridium Spark Plugs

Champion started using iridium 30 years ago, because they realised it was the best material for the job. Today, they are still going strong with iridium spark plugs that perform under pressure. Regardless of engine, manufacturer or ignition type.


Part Numbers: 9407, 9055, 9016, 9403, 9404, 9299, 9013, 9405, 9805, 9006


Features:

  • Iridium center electrode delivers maximum life
  • Fine-wire center electrode for greater excitability
  • V-trimmed ground electrode promotes sharper spark focus

For more products, you can visit our Champion Spark Plug section.

4.5. Autolite Spark Plugs

4.5. Autolite Spark Plugs


Since its inception, the Autolite® brand has provided the automotive aftermarket and Original Equipment manufacturers the highest quality ignition products. They have been in operation for over 100 years and have produced more than 11 billion spark and glow plugs. Their plugs are specifically designed for each application and meet or exceed OE quality and performance. Autolite is a leading supplier of spark plugs and makes plugs for Japanese, European and Korean cars as well as plugs for Lawn & Garden and Power Sports. 

A. Platinum Spark Plugs

Step up to platinum. A center wire platinum firing tip provides improved performance and durability (compared to standard copper plugs). They fire quicker and cleaner with less voltage for easier starts, quicker acceleration and improved fuel economy versus standard plugs. Guaranteed for 4 years.


Part Numbers: AP605, AP103, AP5245, AP3923, AP105, AP45, AP106, AP5145, AP46, AP86 and more.


Features:

  • Platinum center wire firing tip for improved performance.
  • Superconductive Yttrium enhanced ground electrode provides superior heat transfer
  • Full platinum tip ensures virtually no gap erosion for longer plug life
  • Leakproof, heat-fused resistor for durability
  • Cleaner firing and improved efficiency over the life of the plug compared to worn plug
  • High nickel alloy side electrode maintains a precise gap
  • Full platinum tip assures virtually no gap erosion
  • Necked-down center electrode fires quicker, cleaner with less voltage for easier starts, quicker acceleration, and improved fuel economy


B. Double Platinum Spark Plug

Better materials to give your engine better performance. Platinum-to-platinum design greatly decreases gap erosion, reduces misfires, and provides improved durability (compared to standard plugs). It's the superior-performing spark plug, providing preferred technology for DIS engines. Guaranteed for 5 years.


Part Numbers: APP105, APP3924, APP5364, APP5125, APP5503, APP5682, APP646, APP5684, APP3922, APP605, APP103


Features:

  • Platinum-to-platinum firing for superior durability
  • Superconductive Yttrium enhanced ground electrode provides superior heat transfer
  • Platinum enhanced high nickel alloy side electrode maintains a precision gap
  • Platinum tip ensures virtually no gap erosion for longer plug life
  • Maintains optimum performance and fuel economy longer
  • Longer life compared to standard plugs
  • Improved efficiency over the life of the plug compared to worn plug
  • High nickel alloy side electrode
  • Full platinum tips
  • Necked-down center electrode
  • Full copper core center electrode


C. Iridium XP Spark Plug

When you're passionate about performance, you need a technologically advanced plug. Autolite Iridium XP utilizes an iridium-enhanced 0.6 mm fine wire and proprietary platinum sidewire for improved durability (compared to 0.8mm fine wire, multi-electrode design and standard plugs) and a more focused ignition for better overall ignitability (compared to the average of other premium brands) providing optimum performance. Now with a lifetime limited warranty. 


Part Numbers: XP5701, XP5325, XP5363, XP5224, XP606, XP3922, XP5144, XP3924, XP5364, XP26, XP6203, XP5405


Features:

  • Better durability and a more focused ignition for optimum performance.
  • Iridium enhanced 0.6mm fine-wire design for optimal durability and performance
  • Platinum protected ground wire for maximum efficiency in all ignition types including DIS systems
  • V-trimmed ground electrode for improved ignitability
  • Iridium-enhanced center electrode
  • Proprietary, platinum sidewire technology
  • 0.6-mm fine wire design
  • Nickel-plated shell


D. Resistor Copper Spark Plug

Since 1936, Autolite has been a trusted leader and innovator in spark plug technology. You can count on our copper plugs for performance and value, backed by decades of experience and passion. Includes a 2 year limited warranty.


Part Numbers: 306, 63, 5503, 5143, 3926, 5682, 4164, 606, 5245, 765


Features:

  • Improved fuel economy, Smooth acceleration and Lower emissions makes Autolite® Copper Core plugs the industry standard.
  • Guaranteed to deliver quick starts, good fuel economy, and smooth acceleration.
  • Copper core center electrode for higher thermal conductivity
  • Specially engineered high nickel alloy center and ground electrode for extended life
  • High alumina ceramic for high dielectric strength
  • Leakproof, heat-fused internal seal for durability
  • Multi-rib insulator prevents flash-over
  • Guaranteed to deliver quick starts, dependable performance, and smooth acceleration.
  • Superb heat dissipation and durability
  • Copper-glass seal bonds insulator, terminal post center electrode together; assures full required voltage at spark gap; gas-tight seal (100% leak proof)
  • Multi-rib insulator reduces danger of "flash-over"
  • One-piece terminal post adds strength
  • Resistor reduces radio frequency interference (RFI) and electrode erosion
  • Cold-formed steel shell precision rolled threads
  • Full copper core electrode provides better performance in all conditions


E. Non-Resistor Copper Spark Plug

Since 1936, Autolite has been a trusted leader and innovator in spark plug technology. You can count on our copper plugs for performance and value, backed by decades of experience and passion. Includes a 2 year limited warranty.


Part Numbers: 275, 216, 437, 4132, AR51, 373, 295, AR32, AR53, 4093, 216, 4093


Features:

  • Guaranteed to deliver quick starts, good fuel economy, and smooth acceleration.
  • Copper core center electrode for higher thermal conductivity
  • Specially engineered high nickel alloy center and ground electrode for extended life
  • High alumina ceramic for high dielectric strength
  • Leakproof, heat-fused internal seal for durability
  • Multi-rib insulator prevents flash-over
  • Guaranteed to deliver quick starts, dependable performance, and smooth acceleration.
  • Superb heat dissipation and durability
  • Copper-glass seal bonds insulator, terminal post center electrode together; assures full required voltage at spark gap; gas-tight seal (100% leak proof)
  • Multi-rib insulator reduces danger of "flash-over"
  • One-piece terminal post adds strength
  • Resistor reduces radio frequency interference (RFI) and electrode erosion
  • Cold-formed steel shell precision rolled threads
  • Full copper core electrode provides better performance in all conditions
  • Improved fuel economy, Smooth acceleration and Lower emissions makes Autolite® Copper Core plugs the industry standard.

For more products, you can visit our Autolite Spark Plug section.

5. What Are The Symptoms Of Bad Spark Plugs?


Failing to replace the spark plugs in their specified service interval will cause many issues with your engine and vehicle. These signs must not be ignored as this can damage the engine and its components and require more expensive repairs. These are signs to look out for:

A. Car Starting Trouble

A. Car Starting Trouble

The first and most obvious sign of spark plug failure is the inability to cold start the car. Bad spark plugs can be the reason for starting issues and replacing them can lead to easy and quick engine starts.  

B. Engine Misfiring

B. Engine Misfiring

If one or more spark plugs are bust then there is potential for engine misfiring and knocking. This is not just bad for the engine but also various other components. Misfiring engines also increases the pollutants produced which can damage the catalytic converter. 

C. Rough Idle

When idling If you hear knocking or irregular sounds from the engine then the spark may have given out. A rough idle is a vital indication of spark plug failure.

D. Reduced Gas Mileage

D. Reduced Gas Mileage

If the fuel and air mixture is left un-ignited by the spark plug, the fuel simply goes to waste without producing any power which can eventually result in drastically increased fuel consumption.

E. Lousy Acceleration

Another telltale sign of worn-out spark plugs is poor acceleration. The engine creates no power in the power stroke due to the lack of spark from the plug. If you are experiencing sluggish acceleration with the gas pedal floored, then you most likely have bad spark plugs in need of immediate replacement. 


It is always advised to stick to the manufacturer-recommended service intervals for spark plugs so as to get the best performance and gas mileage from your engine. But there are many external factors that can be responsible for premature spark plug failure. This is why it is necessary to know the common symptoms of spark plug failure so as to prevent any major damages to the engine and its components. 

Since ignition coil failure also shows similar symptoms, it is possible that you may instead have bad ignition coils and this guide can help you identify and replace bad ignition coils. 

6. FAQs

Q) What Type Of Spark Plug Is Best?

Spark plugs made with iridium electrodes provide the longest life with optimal performance and hence are usually the ideal replacement spark plug choice for most modern high-tension ignition systems. However, some ignition systems still require copper spark plugs and so it is best to stick to the manufacturer-recommended plugs. 


Q) Do Expensive Spark Plugs Make A Difference?

Every spark plug is made with copper cores but the real difference lies in the materials used as the electrode tips. Some spark plugs are made from precious materials such as platinum, yttrium and iridium which cost more than copper and increase the price of the plugs. These precious materials have better properties like wear resistance and higher conductance than copper which make them more efficient and last longer. Therefore, the increase in price is justified by the enhanced features expensive spark plugs offer. 


Q) Is It Worth Upgrading Spark Plugs?

Upgrading your spark plugs will have many benefits for most drivers since platinum and iridium spark plugs have a longer service life, which requires less maintenance and provides more reliable performance. 


Q) Do Better Spark Plugs Increase Horsepower?

Replacing old spark plugs with new ones will return your vehicle to its peak performance and restore any lost horsepower due to the faulty old plugs. Upgrading to iridium spark plugs can also in most cases provide additional horsepower gains by reducing ignition coil dwell period and increasing the spark capacity which ultimately ignite the fuel air mixture more thoroughly and provides better power. 


Q) How Do I Know Which Spark Plugs I Need?

Refer to the considerations section to understand the best spark plugs for your vehicle. 

Related Topics

Related Topics


                                 Signs to replace the ignition coils                                                             Find the right spark plug for your vehicle

NGK Spark Plugs - Part Number Catalog

Category

Part Numbers

Iridium Plug

4344, 6619, 2667, 0372, 93501, 97138, 6510, 94374, 95332

Platinum Plug

AP26, AP666, AP5426, AP606, AP5245

AP45, AP3923, AP5143, AP5145

Standard Spark Plug

7905, 7957, 7975, 6728, 7907, 7927, 8162, 7422

Bosch Spark Plugs - Part Number Catalog

Category

Part Numbers

Iridium Plug

9654, 9698, 9608, 9609, 96322, 9601, 9652, 9657, 96300, 9661

Double Platinum Plug

8100, 8110, 8122, 8112, 8118, 8104, 8171, 8117, 8160

Platinum Plug

6707, 6703, 6715, 6734, 6724, 6721, 6732, 6725, 6743, 6712

Copper Nickel Plug

7980, 7971, FR7HE02, 8100, FR7NPP332, 9698, 8114, FR8TE2, FR7KPP332, FR8TI332

Denso Spark Plugs - Part Number Catalog

Category

Part Numbers

Iridium Plug

5373, 4717, 4715, 3433, 4710, 3422, 4711, 5376, 3419, 4705, 3370

Double Platinum Plug

5092, 3289, 3229, 3301, 3114, 3302, 3172, 3306, 3239

Champion Spark Plugs - Part Number Catalog

Category

Part Numbers

Iridium Plug

9407, 9055, 9016, 9403, 9404, 9299, 9013, 9405, 9805, 9006

Double Platinum Plug

7440, 7989, 7570, 7034, 7070, 7546, 7983, 7032, 7545, 7340

Platinum Power Plug

3570, 3344, 3318, 3034, 3071, 3017, 3405, 3408, 3346, 3066

Copper Plus® Plug

844, 841, 841S, 302, 306, 801, 844S, 91, 328, 587

Autolite Spark Plugs - Part Number Catalog

Category

Part Numbers

Iridium XP Plug

XP5701, XP5325, XP5363, XP5224, XP606, XP3922, XP5144, XP3924, XP5364, XP26, XP6203, XP5405

Double Platinum Plug

APP105, APP3924, APP5364, APP5125, APP5503, APP5682, APP646, APP5684, APP3922, APP605, APP103

Platinum Plug

AP605, AP103, AP5245, AP3923, AP105, AP45, AP106, AP5145, AP46, AP86

Resistor Copper Plug

306, 63, 5503, 5143, 3926, 5682, 4164, 606, 5245, 765

Non-Resistor Copper Plug

275, 216, 437, 4132, AR51, 373, 295, AR32, AR53, 4093, 216, 4093