Choosing the right spark plugs for your Chrysler 300C HEMI is critical for engine performance, fuel efficiency, and longevity. We researched and compared top options from leading brands, evaluating manufacturer specifications, industry standards, and aggregated owner feedback to help you make an informed decision.
This guide covers seven real products available on Amazon, each with distinct strengths. We analyzed factors like electrode material, heat range, gap design, and compatibility with the HEMI V8. Our evaluations are based on published data and real-world owner experiences, not hands-on testing.
| Photo | Product | Score | Buy |
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NGK (6619) LFR6AIX-11 Iridium IX Best Overall Iridium tip, 0.044 in. gap, heat range 6 |
9.2 | 🛒 Check Price |
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Denso (4504) PK20TT Platinum TT Best Value Twin-tip platinum, 0.044 in. gap, heat range 20 |
8.7 | 🛒 Check Price |
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Champion (7989) Copper Plus Budget Pick Copper core, 0.035 in. gap, heat range 12 |
7.8 | 🛒 Check Price |
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Autolite (5224) XP Iridium Long Life Iridium tip, 0.044 in. gap, heat range 4 |
8.2 | 🛒 Check Price |
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Bosch (4417) Platinum+4 Unique Design Four ground electrodes, platinum center, 0.044 in. gap |
7.5 | 🛒 Check Price |
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ACDelco (41-962) Iridium OE Alternative Iridium tip, 0.040 in. gap, heat range 5 |
8.4 | 🛒 Check Price |
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E3 (E3.52) DiamondFIRE Performance Focus Diamond-shaped ground electrode, 0.045 in. gap, heat range 14 |
7.3 | 🛒 Check Price |
1. NGK (6619) LFR6AIX-11 Iridium IX: Best Overall
The NGK Iridium IX is widely considered the gold standard for the Chrysler 300C HEMI. Based on manufacturer specs, the iridium tip offers superior durability and a sharper spark compared to platinum or copper. Owner feedback consistently highlights improved acceleration and smoother idling after installation. In our evaluation, the heat range 6 is ideal for the 5.7L HEMI, balancing performance and fouling resistance.
However, these plugs come at a higher cost per plug. While the longevity offsets the price for many, budget-conscious owners or those with heavily modified engines may prefer a different heat range. If you need a plug for a stock or mildly tuned HEMI, this is the top pick.
- Iridium center electrode for long life and consistent spark
- Trivalent metal plating prevents corrosion and seizing
- OE recommended for many Chrysler HEMI engines
Pros: Excellent throttle response and idle smoothness; Extended service interval (up to 60,000 miles per owner reports)
Cons: Premium price compared to copper plugs
2. Denso (4504) PK20TT Platinum TT: Best Value
The Denso Platinum TT offers an excellent balance of performance and cost for the Chrysler 300C HEMI. Our research shows the twin-tip design provides reliable ignition over a long service life, typically 60,000 miles per owner reports. The U-groove helps ensure complete combustion, which can improve fuel economy slightly. Many owners on forums report it as a direct replacement that works flawlessly.
However, for those who push their HEMI hard (towing, track days, or forced induction), the iridium options may hold up better. The platinum tips can wear faster under extreme heat. But for most daily drivers, this plug offers exceptional value without compromising reliability.
- Twin-tip design for longer life and consistent spark
- U-groove ground electrode improves flame kernel growth
- Pre-gapped for easy installation
Pros: Very affordable for a platinum plug; Good performance and longevity for daily driving
Cons: Not as durable as iridium in high-stress applications
3. Champion (7989) Copper Plus: Budget Pick
The Champion Copper Plus is the most budget-friendly spark plug for the Chrysler 300C HEMI. In our evaluation, it meets basic OEM specifications and will fire the engine reliably. Owner feedback indicates it is a fine choice for those who don’t mind more frequent changes or have a low-mileage vehicle. The copper core offers excellent electrical conductivity, which can help in cold starts.
However, the copper electrode wears significantly faster than platinum or iridium. In a HEMI that often runs hot, you may need to replace these every 20,000 miles. If you plan to keep the car long-term or drive aggressively, skip this plug. It is best for budget builds or temporary replacements.
- Lowest cost option for the HEMI
- Copper core provides good conductivity
- Wide availability
Pros: Very inexpensive; Works well for stock engines in mild conditions
Cons: Short lifespan (20,000-30,000 miles); Not suitable for modified or high-performance use
4. Autolite (5224) XP Iridium: Long Life
The Autolite XP Iridium is designed for longevity, with a fine-wire iridium center electrode and a platinum side wire. Our research indicates this plug can last up to 100,000 miles under normal driving conditions. Owner feedback on HEMI forums is generally positive, noting smooth operation and easy installation. The heat range 4 is appropriate for the 300C’s 5.7L engine.
However, a few owners have reported that the pre-set gap was off and required re-gapping. Also, the cost is slightly higher than the NGK Iridium IX without a clear performance advantage. If you prioritize maximum service intervals and don’t mind checking the gap, this is a solid choice.
- Fine-wire iridium design for extended life
- Patented platinum side wire for durability
- Pre-gapped, no adjustment needed
Pros: Long service life (up to 100,000 miles per manufacturer); Smooth idle and consistent performance
Cons: Slightly more expensive than NGK Iridium; Some owners report gap inconsistency out of box
5. Bosch (4417) Platinum+4: Unique Design
The Bosch Platinum+4 features a distinctive four-ground electrode design that aims to provide multiple spark paths. In our evaluation, this can be beneficial in engines with ignition system wear. Some owners report improved idle and reduced misfires. However, the design is controversial; many HEMI owners find it offers no advantage over standard single-ground plugs and may even cause hesitation.
Based on aggregated feedback, these plugs are not the top choice for the 300C HEMI. They can be harder to install due to the bulkier tip, and the performance gains are inconsistent. If you have a stock engine and want to try something different, they may work, but we recommend sticking with NGK or Denso for proven reliability.
- Four ground electrodes for multiple spark paths
- Platinum center electrode for durability
- Fits many Chrysler engines
Pros: Unique design may reduce misfires in some engines; Good for older engines with worn ignition systems
Cons: Mixed owner feedback on HEMI performance; Bulkier design can be harder to install in tight spaces
6. ACDelco (41-962) Iridium: OE Alternative
The ACDelco Iridium plug is a strong alternative for the Chrysler 300C HEMI. While ACDelco is a GM brand, this plug’s dimensions and heat range are compatible. Our research shows it offers iridium durability and a ruthenium-enhanced ground electrode for extended life. Owner feedback indicates it performs well, with smooth idle and good throttle response.
However, some owners note that the recommended gap of 0.040 inches is tighter than the usual 0.044 inches for the HEMI. This may require re-gapping for best results. Also, it is not a direct OE replacement, so those seeking factory spec may prefer NGK. If you are comfortable adjusting the gap, this plug offers excellent value and reliability.
- Iridium center electrode for long life
- OE supplier for many GM vehicles, but fits HEMI
- Ruthenium-enhanced ground electrode for durability
Pros: Good build quality and consistent gap; Smooth performance and easy starting
Cons: Not an exact OE replacement for Chrysler; Gap may need adjustment for optimal HEMI operation
7. E3 (E3.52) DiamondFIRE: Performance Focus
The E3 DiamondFIRE spark plug uses a patented diamond-shaped ground electrode to create a larger flame kernel. In theory, this can improve combustion efficiency and power. Some owners on forums report a noticeable increase in throttle response and fuel economy. For those with modified HEMIs, it may offer a performance edge.
However, our evaluation reveals mixed feedback. A significant number of owners have reported misfires, rough idle, or check engine lights after installing these plugs. The unique design can cause issues with the HEMI’s ignition system. We recommend caution and suggest sticking with more conventional designs unless you are willing to experiment. For most 300C owners, this is a risky choice.
- Unique diamond-shaped ground electrode for larger flame kernel
- Copper core for heat dissipation
- Designed for improved fuel efficiency and power
Pros: Innovative design may boost low-end torque; Good for modified engines looking for more spark
Cons: Mixed reliability reports; some owners experienced misfires; Not recommended by many HEMI experts
Frequently Asked Questions
What is the correct spark plug gap for a Chrysler 300C HEMI?
For most 5.7L HEMI engines, the recommended gap is 0.044 inches (1.1 mm). Always verify with your owner’s manual, as some model years may vary. Aftermarket plugs often come pre-gapped, but it’s wise to check with a gap tool before installation.
How often should I change spark plugs on a Chrysler 300C HEMI?
Service intervals depend on the plug type. Copper plugs last about 20,000-30,000 miles, platinum around 60,000 miles, and iridium up to 100,000 miles. However, the HEMI’s high operating temperature can reduce lifespan. We recommend inspecting plugs every 30,000 miles.
Can I use iridium spark plugs in my stock Chrysler 300C HEMI?
Yes, iridium plugs are an excellent upgrade for stock HEMIs. They offer longer life and better performance than standard copper plugs. Ensure the heat range matches the factory specification (usually heat range 6 for NGK). Most owners see improved throttle response and smoother idle.
What happens if I use the wrong heat range spark plug?
Using a plug that is too hot can cause pre-ignition and engine damage, while a plug that is too cold may foul and cause misfires. For the 300C HEMI, stick with the recommended heat range (e.g., NGK heat range 6 or Denso heat range 20). Modified engines may require a colder plug.
Are double platinum spark plugs better than iridium for the HEMI?
Iridium plugs generally have a finer electrode and longer lifespan than double platinum. However, double platinum plugs are more affordable and still offer good durability. For the HEMI, iridium is preferred for performance and longevity, but double platinum is a reliable budget option.
Our Verdict
After researching and comparing the options, the NGK (6619) LFR6AIX-11 Iridium IX is our top pick for the Chrysler 300C HEMI. It offers the best balance of performance, durability, and owner satisfaction. For a more budget-friendly choice that still provides excellent value, the Denso (4504) PK20TT Platinum TT is our runner up.
