Choosing the best spark plugs for 5.7 Hemi engines is crucial for maintaining optimal performance, fuel efficiency, and engine longevity. The 5.7L Hemi V8, found in a wide range of Dodge, Ram, Jeep, and Chrysler vehicles, is a powerhouse that demands the right ignition components to deliver its full potential. From ensuring crisp throttle response to preventing misfires and maximizing horsepower, the quality of your spark plugs plays a significant role.
I understand the importance of making an informed decision, which is why I’ve compiled this comprehensive guide. I’ll delve into the top spark plug options available, examining their unique features, benefits, and ideal applications. My top recommendation, based on a balance of performance, reliability, and user satisfaction, is the 16 Pc NGK Iridium IX Spark Plugs.
Throughout this article, you’ll learn about different spark plug materials, their impact on engine performance, and how to select the perfect set for your specific Hemi model and driving needs. Whether you’re looking to upgrade for enhanced power or simply seeking reliable replacements, this guide will provide the essential information you need.
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Best Spark Plugs for 5.7 Hemi: Quick Comparison
| Product | Name | Price |
|---|---|---|
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16 Pc NGK Iridium IX Spark Plugs | Check Price |
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KAX 8pcs Ignition Coils and 16pcs Iridium | Check Price |
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16 Pc Champion Copper Plus Spark Plugs | Check Price |
 |
Overstockdirect NGK 92145 Laser Iridium Spark Plugs | Check Price |
 |
Ignition Coils and Premium Iridium Spark Plugs | Check Price |
 |
NGK Set of 16 Iridium IX Spark | Check Price |
 |
AIP Electronics Dragon FIRE Performance Ignition Coils | Check Price |
 |
BDFHYK 4024123628 Iridium Spark Plugs Compatible With | Check Price |
 |
Autoexact Ignition Coils and Iridium Spark Plug | Check Price |
 |
Autoexact Ignition Coil Packs and Iridium Spark | Check Price |
10 Best Spark Plugs for 5.7 Hemi: Essential Information Guide
1. 16 Pc NGK Iridium IX Spark Plugs
The NGK Iridium IX spark plugs consistently rank at the top for 5.7 Hemi owners, and for good reason. These are genuine NGK parts, a brand synonymous with quality and innovation in ignition systems. Their ultra-fine 0.6mm iridium tip is specifically designed to sharpen throttle response and acceleration, which is a noticeable benefit for any Hemi driver. With a recommended replacement interval of 40,000-60,000 miles, they offer excellent longevity for a fine-wire performance plug.
What sets these apart is their ability to reduce emissions and misfires. The advanced center and ground electrodes promote a sharper spark focus, leading to more complete and efficient combustion. This translates directly into better engine performance and reliability. They are particularly well-suited for a wide range of Hemi vehicles, including the Ram 1500 5.7L V8 from 2011-2021, making them an excellent choice for those seeking the best spark plugs for 2020 Ram 1500 5.7 Hemi and other recent models. While they are a premium option, the performance gains and durability often justify the investment for enthusiasts and daily drivers alike.
2. KAX 8pcs Ignition Coils and 16pcs Iridium
This KAX kit offers a comprehensive solution by bundling 8 ignition coils and 16 iridium spark plugs, along with a tool kit. This makes it an attractive option for those looking to refresh their entire ignition system at once, which is often recommended for optimal performance and to prevent future issues. The inclusion of a magnetic socket in the tool kit is a thoughtful touch, making spark plug installation and removal significantly easier and safer by preventing dropped parts.
The kit boasts broad vehicle fitment, covering a wide array of 5.7L Hemi vehicles from 2009-2023, including the Ram 1500, Chrysler 300, Challenger, Charger, Durango, Jeep Commander, and Grand Cherokee. This extensive compatibility means it’s a strong contender for the best spark plugs for 2019 Ram 1500 5.7 Hemi, as well as many other popular Hemi applications. Designed as a direct OEM replacement, installation is intended to be straightforward and hassle-free. While buying a complete kit can sometimes mean a slight compromise in individual component performance compared to top-tier standalone parts, the convenience and value of this package are undeniable for many Hemi owners.
3. 16 Pc Champion Copper Plus Spark Plugs
Champion Copper Plus spark plugs represent a classic and reliable choice for 5.7 Hemi engines, especially for those who prioritize value and proven technology. These are genuine Champion parts, a brand with a long history in automotive ignition. Unlike iridium or platinum plugs, copper-core plugs excel at dissipating heat quickly, which can be beneficial for certain engine characteristics. They are known for their consistent performance and are a solid choice for maintaining factory specifications.
While their recommended replacement interval of 20,000-30,000 miles is shorter than that of precious metal plugs, their affordability makes more frequent changes less impactful on the budget. Champion emphasizes their racing heritage, translating that expertise into reliable components for everyday drivers. These plugs are particularly suitable for Ram 1500 5.7L V8 models from 2011-2019, making them a practical and budget-friendly option for the best spark plugs for 2017 Ram 1500 5.7 Hemi and similar years. They are a great choice for owners who prefer traditional copper plugs and are diligent with their maintenance schedule.
4. Overstockdirect NGK 92145 Laser Iridium Spark Plugs
The Overstockdirect NGK 92145 Laser Iridium Spark Plugs offer a premium solution for Hemi owners seeking the ultimate in longevity and performance. As genuine NGK Laser Iridium plugs, they are engineered specifically for OE applications, meaning they meet the stringent quality and durability standards expected by vehicle manufacturers. NGK is a world leader in OEM spark plugs, and this product reflects that expertise.
Laser Iridium plugs feature an iridium-tipped center electrode, which is six times harder than platinum, providing exceptional durability. Many also include a platinum pad on the ground electrode for even wear, especially in distributorless ignition systems common in modern Hemi engines. This construction ensures a long service life and consistent, reliable ignition. Their high-grade alumina ceramic and 98% pure copper core prevent overheating while ensuring dependable starts. With compatibility spanning select 2009-2024 Chrysler, Dodge, Jeep, and Ram 5.7L Hemi V8 models, these are an excellent choice for those prioritizing maximum lifespan and OEM-level quality, making them a top contender for the best spark plugs for 2016 Ram 1500 5.7 Hemi and newer models.
5. Ignition Coils and Premium Iridium Spark Plugs
This comprehensive kit provides 8 ignition coils and 16 premium iridium spark plugs, designed for a direct fit in a wide range of 5.7L Hemi V8 vehicles from 2008-2017. It’s an ideal solution for Hemi owners experiencing misfires, rough idling, or a lit Check Engine Light (CEL) due to failing ignition components. The kit is precision-engineered to directly replace common OEM part numbers like UF504 and LZFR5CI-11, ensuring a hassle-free, drop-in installation without modifications.
The heavy-duty ignition coils are built with silicon-steel cores, high-pressure rubber boots, and imported epoxy and wire, all designed to withstand extreme heat and prevent cracking or voltage leaks. The iridium spark plugs feature ultra-fine tips for a hotter, more focused spark, contributing to improved combustion. This kit is particularly relevant for slightly older Hemi models, such as the best spark plugs for 2015 Ram 1500 5.7 Hemi, offering a complete ignition system overhaul to restore smooth engine operation and address common performance issues. The promise of an easy DIY installation in about 40 minutes with basic tools adds to its appeal for the home mechanic.
6. NGK Set of 16 Iridium IX Spark
This NGK Set of 16 Iridium IX Spark Plugs is another strong offering from the renowned NGK brand, specifically tailored for a broad range of Chrysler, Dodge, Jeep, and Ram vehicles equipped with 5.7L and 6.4L V8 engines. This particular listing highlights compatibility with Ram 1500 models from 2011 all the way up to 2024, emphasizing its relevance for current and recent Hemi owners. As genuine NGK parts, buyers can expect the same high standards of quality and performance that the brand is known for.
The Iridium IX series is characterized by its fine-wire iridium tip, which promotes superior ignitability and a more consistent spark. This design contributes to improved throttle response, better fuel efficiency, and reduced misfires, making it a popular choice for those looking to enhance their Hemi’s overall driving experience. The direct replacement nature of these auto parts means installation should be straightforward for those familiar with spark plug changes. For owners of various Hemi-powered vehicles, including the Ram 1500, this set provides a reliable and performance-oriented upgrade or replacement option.
7. AIP Electronics Dragon FIRE Performance Ignition Coils
The AIP Electronics Dragon FIRE Performance Ignition Coils & Iridium Spark Plugs kit is designed to offer a significant upgrade over standard OEM components, promising up to 15% more energy output. This increased energy translates to a stronger, more consistent spark, which can lead to improved combustion, better throttle response, and potentially enhanced horsepower for your Hemi engine. The kit includes both ignition coils and iridium spark plugs, providing a complete ignition system refresh.
Dragon Fire Performance emphasizes OEM-grade durability, ensuring that while you get performance benefits, you’re not sacrificing reliability. The components are designed as a direct factory replacement, making them “plug and play” for easier installation. Compatibility spans a wide range of 2008-2019 Dodge, Jeep, Chrysler, and Ram vehicles with 5.7L, 5.9L, 6.1L, and 6.4L V8 engines. This broad fitment makes it a versatile option for many Hemi owners looking for a performance boost, including those with the best spark plugs for 5.7 Hemi Challenger, where maximizing engine output is often a priority. It’s a compelling choice for enthusiasts seeking a noticeable performance improvement from their ignition system.
8. BDFHYK 4024123628 Iridium Spark Plugs Compatible With
The BDFHYK 4024123628 Iridium Spark Plugs offer a direct replacement solution for Ram 1500 5.7L V8 models from 2011-2021. This set of 16 iridium spark plugs is presented as a high-quality, OE-level durable auto part, manufactured by a professional auto parts company. The brand highlights superior ignition performance, faster and more sensitive ignition jumps, and a significant increase in power performance, all while efficiently adapting to the needs of the car.
Key features include extremely fine iridium electrodes for good ignition performance and insulators made from isostatic ceramics for high density, strength, and excellent insulation. These design choices contribute to the spark plug’s ability to relieve performance issues and ensure reliable operation. For Ram 1500 owners within the specified years, this BDFHYK set provides a cost-effective alternative to some of the more premium brands, without compromising on the benefits of iridium technology. The emphasis on OE standard performance and durability, backed by TS16949 certification, aims to instill confidence in buyers looking for a reliable replacement.
9. Autoexact Ignition Coils and Iridium Spark Plug
The Autoexact Ignition Coils and Iridium Spark Plug Set provides a complete ignition system overhaul for a broad range of 5.7L V8 Hemi vehicles from 2008-2024. This kit includes 8 ignition coils and 16 pre-gapped iridium spark plugs, making it a convenient and comprehensive solution for addressing common ignition-related symptoms. The brand emphasizes that replacing both coils and plugs together helps reduce repeated repairs and simplifies the maintenance process.
Designed as a direct OEM replacement, this kit aims for an exact fit by year, make, model, and engine, ensuring straightforward installation. The fine-wire iridium spark plugs and epoxy-potted ignition coils are built for stable ignition and consistent spark delivery, using heat-resistant and vibration-resistant construction for reliable daily driving. For Hemi owners experiencing issues like engine misfire, rough idle, hard starting, hesitation, or a check engine light (P0300–P0308 codes), this kit offers a targeted solution to restore peak performance. Its wide compatibility makes it a relevant option for many Hemi models, including the best spark plugs for 5.7 Hemi Challenger, offering a complete refresh for the ignition system.
10. Autoexact Ignition Coil Packs and Iridium Spark
Another strong offering from Autoexact, this kit also bundles 8 ignition coil packs with 16 iridium spark plugs, targeting a wide array of 5.7L V8 Hemi vehicles from 2008-2024, including Ram 1500, 2500, 3500, Dodge Charger, Durango, Challenger, Jeep Grand Cherokee, and Chrysler 300. The primary goal of this set is to restore peak performance, save fuel, and eliminate common issues like misfires and rough idling.
The brand claims that worn ignition parts lead to power loss and wasted fuel, and their high-performance coil and iridium plugs deliver stronger, stabler sparks for full combustion. This translates to smoother acceleration, less engine shaking, and improved fuel economy. The pre-gapped fine-wire iridium spark plugs are rated for up to 40,000 miles, and the epoxy-potted, heat-resistant ignition coils are designed for durability. With 100% OEM fit and a plug-and-play design, along with factory pre-lubrication, installation is intended to be easy for DIYers. This kit is a compelling choice for any Hemi owner looking for a complete, cost-effective ignition system upgrade to address performance issues and enhance overall driving experience.
Understanding the 5.7 HEMI Ignition System
The ignition system is one of the most important components of your 5.7L HEMI engine. Its job is to ignite the air-fuel mixture inside each cylinder at the exact right moment, allowing the engine to produce power efficiently. Even the highest-quality fuel cannot deliver optimal performance if the ignition system isn’t working properly.
Unlike older engines that relied on a distributor, the 5.7 HEMI uses a Coil-on-Plug (COP) ignition system. Each cylinder has its own dedicated ignition coil mounted directly above the spark plug. This design provides a stronger, more consistent spark while reducing energy loss and improving reliability.
Here’s how the ignition process works:
- The engine control module (ECM) calculates the ideal ignition timing.
- It signals the ignition coil for the specific cylinder.
- The coil converts the battery’s 12 volts into tens of thousands of volts.
- The spark plug receives this high voltage and creates a spark across its electrode gap.
- The spark ignites the compressed air-fuel mixture, generating the power that drives the piston.
Because the 5.7 HEMI is a high-compression V8 engine, it depends on consistent spark delivery under a wide range of operating conditions. Whether you’re commuting, towing a trailer, or accelerating hard, properly functioning spark plugs help ensure smooth combustion in every cylinder.
When spark plugs begin to wear, the ignition system must work harder to produce a reliable spark. This can lead to incomplete combustion, reduced fuel efficiency, rough engine operation, and even misfires if left unaddressed.
A healthy ignition system offers several benefits:
- Smooth engine idle
- Faster, more reliable starts
- Better throttle response
- Improved fuel economy
- Reduced emissions
- Consistent engine performance under load
Although ignition coils also wear over time, spark plugs are considered regular maintenance items and should be inspected or replaced according to your vehicle manufacturer’s recommended service interval.
OEM Spark Plug Specifications for 5.7 HEMI
Using the correct spark plug specifications is just as important as choosing a trusted brand. The 5.7 HEMI has been produced for more than two decades, and Chrysler has updated the recommended spark plugs and service intervals over the years. Always verify the specifications for your exact model year before purchasing replacement plugs.
Typical OEM Spark Plug Specifications
| Specification | Details |
| Engine | 5.7L HEMI V8 |
| Spark Plug Type | Copper or Iridium (varies by model year) |
| Electrode Design | Fine-wire center electrode |
| Thread Size | M14 × 1.25 |
| Reach | 26.5 mm (approx.) |
| Hex Size | 5/8 inch (16 mm) |
| Gap | Follow the factory specification for your model year |
| Quantity Required | 16 spark plugs (2 per cylinder) |
Note: Most modern 5.7 HEMI engines use 16 spark plugs, with two plugs installed in each of the engine’s eight cylinders. This dual-plug design improves combustion efficiency, helps reduce emissions, and contributes to smoother engine operation.
OEM Spark Plug Materials by Model Year
| Model Year | Typical OEM Material | Expected Service Life |
| 2003–2008 | Copper | Around 30,000 miles |
| 2009–2014 | Copper or Platinum (varies by application) | 30,000–60,000 miles |
| 2015 and newer | Iridium | Up to 100,000 miles (under normal driving conditions) |
The exact OEM part number may vary depending on the vehicle. For example, a 5.7 HEMI in a Ram 1500 may use a different factory spark plug than the same engine installed in a Dodge Charger or Jeep Grand Cherokee. Always confirm compatibility using your vehicle’s VIN or owner’s manual before ordering replacement plugs.
Why OEM Specifications Matter
Choosing a spark plug that matches the factory specifications helps ensure:
- Proper ignition timing and combustion
- Reliable cold starts
- Maximum fuel efficiency
- Reduced risk of engine misfires
- Long ignition coil life
- Consistent performance under heavy loads
While many aftermarket spark plugs exceed OEM quality, they should still match the correct thread size, heat range, reach, and electrode design specified for your particular 5.7 HEMI engine. Using the wrong spark plug can negatively affect performance and, in some cases, lead to engine damage over time.
Which Spark Plug Material Is Best for a 5.7 HEMI?
Not all spark plugs are made from the same materials, and the type of electrode used has a direct impact on performance, durability, and replacement intervals. While all spark plugs perform the same basic function—igniting the air-fuel mixture—their lifespan and overall performance can vary significantly.
For most modern 5.7 HEMI engines, iridium spark plugs are the best overall choice because they offer the longest service life and maintain a strong, consistent spark even after thousands of miles. However, the best material ultimately depends on your driving habits, budget, and your vehicle’s factory recommendations.
Spark Plug Materials Compared
| Material | Lifespan | Performance | Price | Best For |
| Copper | 20,000–30,000 miles | Excellent conductivity but wears quickly | $ | Older HEMI engines and budget replacements |
| Platinum | 50,000–60,000 miles | Better durability than copper | $$ | Daily drivers seeking longer service intervals |
| Double Platinum | 60,000–80,000 miles | Improved wear resistance | $$$ | High-mileage vehicles with extended maintenance intervals |
| Iridium | Up to 100,000 miles | Outstanding durability and consistent ignition | $$$$ | Most modern 5.7 HEMI engines and long-term ownership |
Copper Spark Plugs
Copper spark plugs conduct electricity exceptionally well, which helps create a strong spark. However, copper electrodes wear much faster than platinum or iridium, requiring more frequent replacement. They are commonly found in earlier 5.7 HEMI models that originally came equipped with copper plugs.
Pros
- Lowest purchase cost
- Excellent electrical conductivity
- Good choice for older OEM applications
Cons
- Shortest lifespan
- Requires more frequent maintenance
Platinum Spark Plugs
Platinum plugs feature a harder electrode material that resists wear better than copper. They strike a balance between affordability and longevity, making them a practical option for many daily-driven vehicles.
Pros
- Longer lifespan than copper
- Better resistance to wear
- Reduced maintenance frequency
Cons
- Higher cost than copper
- Not as durable as iridium
Double Platinum Spark Plugs
Double platinum spark plugs use platinum on both the center and ground electrodes, improving durability even further. They are designed for engines that demand greater resistance to electrode wear over long service intervals.
Pros
- Extended service life
- Reliable long-term performance
- Excellent for high-mileage vehicles
Cons
- More expensive than standard platinum
- Still doesn’t last as long as iridium
Iridium Spark Plugs
Iridium is one of the hardest and most heat-resistant materials used in spark plugs. Its fine-wire center electrode requires less voltage to produce a spark while maintaining excellent durability. This makes iridium the preferred choice for most late-model 5.7 HEMI engines.
Pros
- Longest service life
- Excellent ignition performance
- Better resistance to heat and wear
- Less frequent replacement
Cons
- Highest initial cost
Which Material Should You Choose?
- Choose copper if your older 5.7 HEMI originally came with copper plugs and you don’t mind more frequent maintenance.
- Choose platinum if you want a balance between price and longevity.
- Choose double platinum if you’re looking for improved durability over standard platinum.
- Choose iridium if you want the longest-lasting, lowest-maintenance option and your vehicle manufacturer recommends it.
Signs Your 5.7 HEMI Needs New Spark Plugs
Spark plugs gradually wear with every ignition cycle. As the electrodes erode, they require more voltage to produce a spark, making combustion less efficient. Fortunately, your 5.7 HEMI usually provides several warning signs before worn spark plugs become a serious problem.
Recognizing these symptoms early can help you avoid reduced performance, poor fuel economy, and expensive repairs.
Rough Idle
If the engine shakes, vibrates, or feels uneven while idling, worn spark plugs may not be igniting the air-fuel mixture consistently.
Engine Misfires
One of the most common symptoms is an engine misfire. You may notice hesitation, jerking during acceleration, or a flashing Check Engine Light. Ignoring persistent misfires can eventually damage the catalytic converter.
Hard Starting
A healthy ignition system should start the engine quickly. If your 5.7 HEMI takes longer to crank or struggles to start—especially in cold weather—worn spark plugs could be the cause.
Reduced Fuel Economy
Incomplete combustion wastes fuel. If you’ve noticed a drop in miles per gallon without changing your driving habits, aging spark plugs may be contributing to the problem.
Sluggish Acceleration
Slow throttle response or reduced engine power often occurs when spark plugs cannot consistently ignite the fuel mixture under load.
Check Engine Light
Misfires caused by worn spark plugs commonly trigger the Check Engine Light. Diagnostic trouble codes such as P0300 (random misfire) or P0301–P0308 (cylinder-specific misfires) may indicate an ignition-related issue, although other components can also cause these codes.
Increased Exhaust Emissions
Faulty spark plugs can leave fuel unburned during combustion, increasing exhaust emissions and potentially causing your vehicle to fail an emissions inspection.
Poor Towing or Heavy-Load Performance
If your truck feels underpowered while towing or hauling heavy loads, worn spark plugs may be reducing combustion efficiency when the engine is under greater stress.
When Should You Inspect Your Spark Plugs?
Consider inspecting your spark plugs if you notice any of these symptoms or if your vehicle has reached the manufacturer’s recommended replacement interval. Even if only one plug appears worn, replacing the complete set is generally recommended to maintain balanced engine performance across all cylinders.
When Should You Replace Spark Plugs on a 5.7 HEMI?
Spark plugs don’t last forever. Every time your 5.7 HEMI engine fires, the spark plug electrodes experience extreme heat and electrical stress. Over time, the electrodes wear down, the spark becomes weaker, and engine performance gradually declines.
The ideal replacement interval depends on the type of spark plug installed, your driving conditions, and your vehicle’s model year. While some iridium plugs can last up to 100,000 miles, many older HEMI engines equipped with copper plugs require replacement much sooner.
General Replacement Intervals
| Spark Plug Material | Recommended Replacement Interval |
| Copper | Every 20,000–30,000 miles |
| Platinum | Every 50,000–60,000 miles |
| Double Platinum | Every 60,000–80,000 miles |
| Iridium | Up to 100,000 miles |
Note: Always follow the maintenance schedule listed in your owner’s manual, as recommendations can vary by model year and vehicle application.
Factors That Can Shorten Spark Plug Life
Even premium spark plugs may need replacement earlier if your vehicle is driven under demanding conditions, such as:
- Frequent towing or hauling heavy loads
- Stop-and-go city driving
- Short trips where the engine rarely reaches operating temperature
- Off-road driving in dusty or muddy environments
- Aggressive acceleration or performance driving
- Engine modifications that increase cylinder temperatures
Under these conditions, it’s a good idea to inspect the spark plugs periodically rather than waiting for the maximum service interval.
Why You Shouldn’t Delay Replacement
Ignoring worn spark plugs can lead to several problems, including:
- Reduced fuel economy
- Rough idle and engine hesitation
- Loss of power during acceleration
- Increased emissions
- Engine misfires
- Premature ignition coil wear
- Potential catalytic converter damage from prolonged misfires
Replacing spark plugs on time is one of the simplest and most cost-effective ways to keep your 5.7 HEMI running smoothly and avoid more expensive ignition system repairs.
Spark Plug Gap for a 5.7 HEMI
The spark plug gap is the distance between the center electrode and the ground electrode. This small gap is where the electrical spark jumps to ignite the air-fuel mixture inside the combustion chamber.
Although the gap may seem like a minor detail, it has a significant impact on engine performance. A gap that’s too wide or too narrow can cause weak combustion, poor fuel economy, hard starts, and engine misfires.
What Is the Correct Spark Plug Gap?
The correct gap depends on your specific 5.7 HEMI model year and the spark plug being used. Always verify the factory specification in your owner’s manual or the spark plug manufacturer’s application guide before installation.
Many replacement spark plugs come pre-gapped, but they should still be checked before installation because shipping and handling can occasionally alter the gap.
What Happens If the Gap Is Incorrect?
Gap Too Wide
A spark plug gap that’s too wide requires more voltage to produce a spark. This can result in:
- Hard starting
- Engine misfires
- Rough idle
- Reduced fuel economy
- Extra stress on ignition coils
Gap Too Narrow
If the gap is too small, the spark may be weaker and combustion less efficient, leading to:
- Reduced engine power
- Poor throttle response
- Incomplete combustion
- Increased exhaust emissions
Should You Re-Gap Iridium Spark Plugs?
In most cases, avoid adjusting the gap on fine-wire iridium spark plugs unless the manufacturer specifically instructs you to do so. The delicate iridium center electrode can be damaged if improper tools or techniques are used.
Instead:
- Check the gap with a wire-style gap gauge.
- If the measurement is outside the manufacturer’s specification, replace the spark plug or follow the manufacturer’s instructions for adjustment.
Tips for Checking Spark Plug Gap
Before installing new spark plugs:
- Verify the correct gap specification for your engine.
- Use a quality wire-type spark plug gap gauge for accurate measurement.
- Inspect each plug individually, even if it’s labeled as pre-gapped.
- Never force the ground electrode against the fine-wire center electrode, especially on iridium plugs.
Taking a few extra minutes to verify the spark plug gap can help ensure smooth engine operation, reliable starting, and maximum performance from your 5.7 HEMI.
How to Choose the Best Spark Plug for a 5.7 HEMI
With dozens of spark plug options available, choosing the right one for your 5.7 HEMI can feel overwhelming. While many aftermarket plugs claim to improve performance, the best choice is the one that matches your engine’s specifications, driving habits, and maintenance expectations.
Before buying a new set of spark plugs, consider the following factors.
Check Your Vehicle’s Model Year
The 5.7 HEMI has been used in several vehicles over the years, including the Ram 1500, Dodge Charger, Challenger, Durango, Jeep Grand Cherokee, and Chrysler 300. Spark plug recommendations can vary depending on the model year and application.
Always confirm compatibility using your vehicle’s owner’s manual, VIN, or the manufacturer’s parts catalog before ordering.
Choose the Right Electrode Material
Different materials offer different advantages.
- Copper: Best for older HEMI engines that originally used copper plugs.
- Platinum: A good balance of price and durability.
- Double Platinum: Longer service life with improved wear resistance.
- Iridium: Best overall for most modern 5.7 HEMI engines due to its exceptional longevity and reliable ignition performance.
Match the OEM Specifications
Even the highest-rated spark plug isn’t the right choice if it doesn’t match your engine’s specifications.
Make sure the replacement plug has the correct:
- Thread size
- Reach
- Heat range
- Electrode design
- Gap (or can be adjusted to the factory specification)
Using an incorrect spark plug may cause poor performance, engine knocking, or ignition problems.
Consider Your Driving Style
How you use your vehicle also affects the best spark plug choice.
| Driving Style | Recommended Spark Plug |
| Daily commuting | OEM-quality Iridium |
| Long highway trips | Iridium |
| Heavy towing | Premium Iridium |
| Performance driving | Performance Iridium (OEM heat range unless modified) |
| Older high-mileage truck | OEM replacement Copper or Platinum |
Don’t Buy Based on Marketing Claims
Some manufacturers advertise large horsepower gains from premium spark plugs. In reality, replacing worn spark plugs with new, properly specified ones restores lost performance rather than creating significant additional power on an otherwise stock engine.
Focus on:
- OEM compatibility
- Build quality
- Trusted brands
- Long-term reliability
instead of exaggerated performance claims.
Buy From Trusted Brands
Choosing a reputable manufacturer helps ensure consistent quality and proper fitment.
Some of the most trusted spark plug brands for the 5.7 HEMI include:
- NGK
- Champion
- Denso
- Bosch
- Autolite
These brands offer OEM and premium aftermarket options for most 5.7 HEMI applications.
Can You Upgrade From Copper to Iridium Spark Plugs?
Yes—in many cases, you can upgrade from copper to iridium spark plugs as long as the replacement plugs are designed for your specific 5.7 HEMI engine and meet the correct OEM specifications.
Many owners choose iridium plugs because they last significantly longer and require less maintenance than traditional copper plugs. However, an upgrade isn’t always necessary or beneficial for every vehicle.
Benefits of Upgrading to Iridium
Iridium spark plugs offer several advantages over copper plugs.
Longer Service Life
The biggest benefit is durability. While copper plugs may need replacement every 20,000 to 30,000 miles, iridium plugs can often last up to 100,000 miles under normal driving conditions.
More Consistent Ignition Performance
Iridium’s fine-wire center electrode requires less voltage to generate a spark, helping maintain reliable ignition as the plug ages.
Reduced Maintenance
Because they last much longer, iridium plugs reduce maintenance costs and the time spent replacing spark plugs.
Better Resistance to Heat and Wear
Iridium is extremely hard and heat-resistant, making it ideal for high-temperature combustion environments like the 5.7 HEMI.
Are There Any Downsides?
The primary drawback is the higher upfront cost. Iridium spark plugs typically cost more than copper or platinum plugs, although their longer lifespan often offsets the initial expense.
Also, upgrading to iridium will not dramatically increase horsepower or fuel economy if your current spark plugs are already in good condition. The main benefits are longevity, reliability, and reduced maintenance.
When Should You Stay With Copper?
Sticking with copper spark plugs may be the better choice if:
- Your owner’s manual specifically recommends copper plugs.
- You’re restoring an older vehicle and want to maintain factory-original specifications.
- You don’t mind replacing spark plugs more frequently.
- You’re looking for the lowest initial replacement cost.
Final Recommendation
For most late-model 5.7 HEMI engines, high-quality iridium spark plugs are the best long-term investment thanks to their exceptional durability and consistent performance.
However, if your vehicle originally came with copper plugs, the safest approach is to follow the manufacturer’s recommendation or choose an approved upgrade from a reputable brand that matches the correct heat range, thread size, reach, and gap specifications.
Best Spark Plugs for Different 5.7 HEMI Driving Needs
The best spark plug isn’t necessarily the most expensive one—it’s the one that best matches how you use your 5.7 HEMI. Whether you drive your truck every day, tow heavy trailers, or simply want the longest-lasting replacement, certain spark plugs are better suited for specific situations.
The table below summarizes the best options based on different driving needs.
| Use Case | Recommended Type | Why It’s a Good Choice |
| Best Overall | OEM-Quality Iridium | Excellent balance of performance, reliability, and longevity |
| Best Budget Option | Copper | Affordable replacement for older HEMI engines |
| Best OEM Replacement | Same OEM Brand & Specification | Maintains factory performance and compatibility |
| Best for Heavy Towing | Premium Iridium | Handles high combustion temperatures and extended workloads |
| Best for Daily Driving | Iridium or Platinum | Reliable ignition with minimal maintenance |
| Best Performance Build | Performance Iridium (Correct Heat Range) | Consistent spark under higher engine loads |
| Best for High-Mileage Vehicles | Double Platinum or Iridium | Long service life and dependable ignition |
| Lowest Maintenance | Iridium | Can last up to 100,000 miles under normal driving conditions |
Best Overall
If you’re looking for a spark plug that delivers dependable performance in almost every situation, an OEM-quality iridium spark plug is the safest choice. It offers excellent durability, reliable cold starts, consistent combustion, and the longest service life.
Best Budget Option
For owners of older 5.7 HEMI engines, copper spark plugs remain an affordable replacement. While they require more frequent replacement, they provide excellent conductivity and are often the factory-installed option on early model years.
Best for Towing and Heavy Loads
Vehicles that regularly tow trailers or haul heavy cargo generate higher combustion temperatures. Premium iridium spark plugs are better equipped to withstand these conditions while maintaining a consistent spark over long periods.
Best for Long-Term Ownership
If you plan to keep your vehicle for many years, investing in a quality set of iridium spark plugs can reduce maintenance costs and minimize future replacements.
Remember
The “best” spark plug is always one that:
- Matches your vehicle’s OEM specifications
- Fits your model year correctly
- Uses the proper heat range
- Comes from a trusted manufacturer
- Is appropriate for your driving conditions
Common Spark Plug Mistakes to Avoid
Even the highest-quality spark plugs can cause problems if they’re installed incorrectly or if the wrong type is selected. Avoiding a few common mistakes can help maximize performance, fuel efficiency, and engine reliability.
Buying the Wrong Spark Plug
Not all spark plugs fit every 5.7 HEMI. Differences in model year, thread length, heat range, and electrode design mean that choosing the wrong plug can negatively affect engine performance.
Always verify compatibility before purchasing.
Ignoring the Spark Plug Gap
Many replacement spark plugs are advertised as pre-gapped, but it’s still important to check each one before installation.
An incorrect gap can lead to:
- Engine misfires
- Hard starting
- Poor fuel economy
- Rough idle
- Reduced performance
Over-Tightening the Spark Plugs
Applying excessive torque can damage the spark plug threads or even crack the cylinder head.
Using a torque wrench and following the manufacturer’s recommended torque specification helps ensure proper installation.
Under-Tightening the Spark Plugs
Spark plugs that aren’t tightened enough may loosen over time, causing poor heat transfer, combustion leaks, and possible thread damage.
Proper torque is just as important as avoiding over-tightening.
Choosing the Wrong Heat Range
The heat range determines how quickly a spark plug transfers heat away from the combustion chamber.
Using an incorrect heat range may cause:
- Pre-ignition
- Spark plug fouling
- Engine knocking
- Reduced performance
Unless your engine has been professionally modified, it’s usually best to stick with the OEM-recommended heat range.
Mixing Different Spark Plug Types
Installing different brands or different electrode materials in the same engine can result in uneven combustion and inconsistent performance.
Replace all spark plugs with the same type and specification whenever possible.
Skipping Spark Plug Inspections
Even long-life iridium spark plugs should be inspected periodically, especially if you notice symptoms such as rough idle, poor acceleration, or reduced fuel economy.
Regular inspections can help identify problems before they lead to ignition coil failures or catalytic converter damage.
Buying Counterfeit Spark Plugs
Counterfeit spark plugs have become increasingly common in online marketplaces. They may look identical to genuine products but often use inferior materials that wear out quickly.
To reduce the risk of purchasing fake spark plugs:
- Buy from authorized dealers or reputable retailers.
- Check the packaging for signs of tampering.
- Verify the part number matches your vehicle.
- Avoid prices that seem unusually low.
Taking a few extra minutes to choose the correct spark plugs and install them properly can help your 5.7 HEMI deliver reliable performance for thousands of miles.
Spark Plug Installation Tips for a 5.7 HEMI
Installing new spark plugs isn’t particularly complicated, but doing the job correctly is essential for long-term engine performance and reliability. A small installation mistake—such as using the wrong torque or damaging the spark plug gap—can lead to misfires, poor fuel economy, or even costly engine repairs.
Before starting, always allow the engine to cool completely to avoid damaging the aluminum cylinder heads or burning yourself during the replacement process.
Use the Correct Spark Plug Socket
A 5/8-inch (16 mm) spark plug socket is commonly used on most 5.7 HEMI engines. A socket with a rubber insert or magnetic core helps securely hold the spark plug during removal and installation.
You may also need:
- Ratchet
- Extension bar
- Torque wrench
- Spark plug gap gauge
- Compressed air (optional)
Clean Around the Spark Plug Wells
Before removing the old spark plugs, blow compressed air around each spark plug well to remove dirt, sand, or debris.
This prevents contaminants from falling into the combustion chamber after the spark plug is removed.
Check the Gap Before Installation
Even if the spark plugs are labeled as pre-gapped, inspect each one using a wire-style gap gauge.
Shipping and handling can occasionally alter the gap, and verifying it beforehand helps ensure optimal engine performance.
Thread the Spark Plug by Hand First
Always start threading the spark plug by hand rather than using a ratchet immediately.
This greatly reduces the risk of cross-threading, which can permanently damage the aluminum cylinder head.
If the plug doesn’t thread smoothly, remove it and start again instead of forcing it.
Tighten to the Correct Torque
Once the spark plug is seated, tighten it using a torque wrench according to the manufacturer’s recommended specification.
Proper torque ensures:
- Good heat transfer
- Secure sealing
- Correct combustion chamber pressure
- Reduced risk of thread damage
Avoid both over-tightening and under-tightening.
Should You Use Anti-Seize?
Many modern spark plugs come with nickel- or zinc-plated threads, and most manufacturers do not recommend applying anti-seize compound.
Adding anti-seize can alter the torque reading and increase the risk of over-tightening.
Unless the spark plug manufacturer specifically recommends it, install the plugs with clean, dry threads.
Apply Dielectric Grease (Optional)
A small amount of dielectric grease inside the ignition coil boot can help:
- Prevent moisture intrusion
- Reduce corrosion
- Make future spark plug removal easier
Avoid getting dielectric grease on the spark plug electrodes or threads.
Replace One Cylinder at a Time
To avoid mixing up ignition coils or connectors, replace the spark plugs one cylinder at a time.
This simple approach reduces the chance of installation errors and helps ensure everything is reassembled correctly.
Final Installation Checklist
Before starting the engine, make sure you have:
- ✔ Installed the correct spark plugs
- ✔ Verified the spark plug gap
- ✔ Tightened each plug to the proper torque
- ✔ Fully seated every ignition coil
- ✔ Reconnected all electrical connectors
- ✔ Removed all tools from the engine bay
Taking a careful, methodical approach during installation helps your new spark plugs deliver reliable performance for years to come.
Frequently Asked Questions (FAQs)
How many spark plugs does a 5.7 HEMI have?
Most 5.7 HEMI engines use 16 spark plugs—two spark plugs for each of the engine’s eight cylinders. This dual-plug ignition system improves combustion efficiency, helps reduce emissions, and contributes to smoother engine performance.
What are the best spark plugs for a 5.7 HEMI?
The best spark plugs are those that match your vehicle’s OEM specifications. High-quality options from brands like NGK, Champion, Denso, Bosch, and Autolite are popular choices, with iridium models generally offering the longest service life for modern 5.7 HEMI engines.
How often should I replace spark plugs on a 5.7 HEMI?
Replacement intervals depend on the spark plug material:
- Copper: 20,000–30,000 miles
- Platinum: 50,000–60,000 miles
- Double Platinum: 60,000–80,000 miles
- Iridium: Up to 100,000 miles
Always follow your vehicle manufacturer’s maintenance schedule for the most accurate recommendation.
Can bad spark plugs cause engine misfires?
Yes. Worn or damaged spark plugs are one of the most common causes of engine misfires. Other symptoms may include rough idling, poor acceleration, hard starting, reduced fuel economy, and an illuminated Check Engine Light.
Can new spark plugs improve fuel economy?
If your existing spark plugs are worn, replacing them can restore proper combustion and improve fuel efficiency. However, replacing healthy spark plugs with premium models typically won’t produce dramatic gains in MPG.
Should I replace the ignition coils at the same time?
Not necessarily. Ignition coils don’t require routine replacement like spark plugs. However, if a coil has failed, shows signs of damage, or has high mileage, replacing it while changing the spark plugs can save labor in the future.
Can I install iridium spark plugs in an older 5.7 HEMI?
In many cases, yes—as long as the iridium spark plugs are designed for your specific engine and meet the correct OEM specifications, including thread size, reach, heat range, and gap.
Are expensive spark plugs worth it?
Premium spark plugs, particularly iridium models, are often worth the higher initial cost because they last much longer and require less maintenance. However, they won’t significantly increase horsepower in a stock engine.
Do spark plugs increase horsepower?
New spark plugs can restore lost engine performance if the old ones are worn. However, replacing properly functioning spark plugs with premium versions alone is unlikely to produce a noticeable horsepower increase.
What’s the biggest mistake to avoid when replacing spark plugs?
One of the most common mistakes is installing the wrong spark plug or tightening it incorrectly. Always verify compatibility, check the spark plug gap, and tighten each plug to the manufacturer’s recommended torque specification for the best results.
Choosing the best spark plugs for your 5.7 HEMI comes down to selecting the right combination of compatibility, durability, and performance. While there are plenty of quality options available, the ideal spark plug should always match your engine’s OEM specifications and your driving needs.
If you’re looking for the best overall value, a high-quality iridium spark plug is typically the top choice for most modern 5.7 HEMI engines. It offers excellent ignition performance, a long service life, and requires less maintenance than copper or platinum alternatives. On the other hand, if you own an older HEMI that originally came with copper plugs, sticking with an OEM-style replacement may be the most practical option.
Before making your purchase, remember to verify your vehicle’s model year, spark plug compatibility, heat range, and factory specifications. Installing the correct spark plugs—and replacing them at the recommended service interval—can help improve engine reliability, maintain fuel efficiency, and reduce the risk of misfires or costly ignition system repairs.
Whether you drive a Ram 1500, Dodge Charger, Challenger, Durango, Jeep Grand Cherokee, or Chrysler 300 with a 5.7 HEMI, any of the products reviewed in this guide can be a solid choice when matched to your vehicle’s requirements.
Hopefully, this guide has helped you narrow down the best option for your needs and made it easier to choose the right spark plugs with confidence. By investing in quality replacement plugs today, you’ll help keep your 5.7 HEMI running smoothly for thousands of miles to come.