Best Spark Plugs For 2004 GMC Envoy

When I noticed my old 2004 GMC Envoy L6 4.2L was starting to sound a bit rougher at idle, and the gas mileage wasn’t what it used to be, I knew exactly where to start: the spark plugs. For the robust inline-six engine in the Envoy, having the right plug is critical for smooth operation and longevity. We’re looking for a balance of durability, performance, and value. Finding high-quality Best Spark Plugs For 2004 GMC Envoy replacements doesn’t have to be confusing, though. This guide compiles seven excellent options, covering everything from OEM parts to high-performance iridium kits, helping you restore that smooth, factory-fresh ride.

IMAGE	PRODUCT NAME	AMAZON LINK
	A-Premium Iridium Platinum Spark Plugs Compatible with…	View on Amazon
	Set of 6 Ignition Coil Pack and Spark Plugs Iridium…	View on Amazon
	Iridium Spark Plugs 6 Pack 91418 Fits for 2014-2021 Chevy…	View on Amazon
	NGK G-Power Platinum Spark Plug LTR5GP (6 Pack) for GMC…	View on Amazon
	UF303 Ignition Coil Pack and Iridium Spark Plugs Set of…	View on Amazon
	Iridium Spark Plugs 6 Pack Compatible with Chevrolet…	View on Amazon
	ACDelco GM Original Equipment 41-962 (19299585) Double…	View on Amazon

A-Premium Iridium Platinum Spark Plugs Compatible with Chevrolet Silverado 1500, Express 2500/3500, Trailblazer & GMC Sierra, Savana, Envoy & Buick Rainier & Isuzu Ascender & Oldsmobile, Pack of 6

These A-Premium plugs offer a powerful combination of both iridium and platinum, giving you extended life and reliable performance tailored for a wide range of GM vehicles, including the 2004 Envoy. The iridium center electrode is exceptionally durable, while the platinum core material ensures a consistent spark and helps resist fouling. They are engineered to last, recommending replacement intervals between 80,000 to 100,000 miles, which is ideal if you want a set-it-and-forget-it solution.

Key features that stand out:
– Hybrid Durability: Features both Iridium center tip and Platinum core material for superior lifespan.
– High Resistance: Excellent durability against heat and electrical wear, perfect for the 4.2L L6 engine.
– Specifications Provided: Detailed specs like gap size (often pre-set to 0.044 inches for the 4.2L) and thread diameter are clearly listed.

• Pros: Extremely long lifespan; excellent heat transfer; proven fitment for the L6 4.2L engine family.
• Cons: Being a premium material blend, the initial cost is higher than standard copper plugs.
• Best for: Drivers prioritizing maximum longevity and minimum maintenance cycles.

Expert Opinion: The use of Iridium/Platinum makes this plug highly resistant to degradation, maintaining the required voltage and spark stability across huge mileage intervals. Always double-check the pre-set gap against your specific vehicle’s owner’s manual or shop manual, as the 2004 Envoy might require a slight adjustment depending on the exact build date.

Set of 6 Ignition Coil Pack and Spark Plugs Iridium Compatible with 2002 2003 2004 2005 Chevy Trailblazer GMC Envoy Ascender Bravada Buick Rainier 9-7X 4.2L L6 Spark Plug Coils Replaces# UF303 41103

Sometimes, when you replace the spark plugs on a high-mileage 2004 Envoy, it’s smart to refresh the entire ignition system, especially if you’ve noticed misfires. This comprehensive kit provides six iridium spark plugs along with six matching UF303 ignition coil packs. This saves you the hassle of cross-referencing parts and ensures that both the coils and the plugs are designed to work perfectly together, restoring peak firing efficiency immediately.

Key features that stand out:
– Complete Kit: Includes both ignition coils (UF303 replacement) and Iridium spark plugs.
– Direct Fit: Designed specifically for the GMT360 platform (Envoy, Trailblazer, Ascender) with the 4.2L L6 engine.
– Warranty: Comes backed by a solid 24-month warranty for peace of mind.

• Pros: Excellent value by combining two critical maintenance items; guarantees system compatibility; direct plug-and-play installation.
• Cons: The quality of aftermarket coils can sometimes be inconsistent compared to high-end OEM.
• Best for: Budget-conscious owners looking to completely overhaul their ignition system in one go.

Expert Opinion: When dealing with misfires, it’s often hard to tell if the coil or the plug is the culprit. This kit eliminates the guesswork. While iridium plugs offer great performance, the primary benefit here is the convenience and cost savings of bundling the coils, which are known failure points in the 4.2L engine over time.

Iridium Spark Plugs 6 Pack 91418 Fits for 2014-2021 Chevy Silverado 1500 4.3 V6 GMC Sierra, Chevrolet Trailblazer GMC Envoy 4.2 2002 2003 2004 2005 2006 2007 2008 2009 Replaces 12622441, 41-114

This iridium plug set focuses heavily on maximizing engine output and fuel economy. By utilizing a 0.6mm fine-wire iridium centerwire tip and advanced laser welding, these plugs generate a highly focused and powerful spark. This improved combustion efficiency means your 2004 Envoy should see an immediate positive change in throttle response and potentially better MPG numbers.

Key features that stand out:
– Fine Wire Technology: 0.6mm iridium centerwire maximizes spark concentration and reduces voltage requirements.
– Exceptional Fuel Efficiency: Designed to help the engine operate at peak performance, minimizing consumption.
– Extreme Durability: Iridium is six times harder than platinum, ensuring long-lasting performance in high-heat conditions.

• Pros: Superior combustion leading to better throttle response; robust construction; competitive pricing for a 6-pack of iridium.
• Cons: Less information provided on the specific manufacturer quality control standards compared to top-tier brands.
• Best for: Drivers focused on squeezing every ounce of power and efficiency out of the Envoy’s L6 motor.

Expert Opinion: The fine-wire design is a legitimate performance booster. The smaller electrode tip requires less energy to jump the gap, resulting in fewer misfires under load and overall cleaner combustion, which is crucial for maintaining engine health in an older vehicle like the 2004 Envoy.

NGK G-Power Platinum Spark Plug LTR5GP (6 Pack) for GMC ENVOY XL SLT 2002-2006 4.2L/256

NGK is a globally trusted name in ignition components, and the G-Power Platinum line is a fantastic choice for anyone seeking reliable, OEM-grade quality without the high price tag of iridium. These plugs utilize a fine-wire platinum tip, which provides a superior anti-seizing and anti-corrosion barrier thanks to the trivalent metal plating. For the 2004 Envoy, these will deliver consistent starting power and reliable service life, matching factory standards closely.

Key features that stand out:
– Platinum Tipped Electrode: Fine wire design reduces required voltage for quick starts and better acceleration.
– Corrosion Resistance: Trivalent metal plating prevents rust and seizing, making future plug changes easier.
– Heat Management: Pure alumina silicate ceramic insulator and copper core aid in excellent heat transfer away from the tip.

• Pros: Trusted brand reputation; excellent value for platinum plugs; superior anti-seizing properties; highly consistent performance.
• Cons: Platinum plugs don’t have the extreme lifespan of modern iridium options.
• Best for: Owners who prefer a reliable, mid-range plug from a premium brand that focuses on consistent, smooth operation.

Expert Opinion: NGK’s reputation is unmatched. While these aren’t the longest-lasting plugs on this list, they are incredibly reliable and consistent throughout their service life. For the L6 4.2L, the NGK LTR5GP is often a preferred plug among mechanics for its ability to prevent leakage and ensure optimal heat range.

UF303 Ignition Coil Pack and Iridium Spark Plugs Set of 6 Compatible with 2002 2003 2004 2005 Chevy Trailblazer GMC Envoy Isuzu Ascender Olds Bravada Buick Rainier Saab 9-7X 4.2L L6,Replace#,12568062

Similar to the second option, this kit bundles six UF303 coil packs with six iridium spark plugs, but it emphasizes performance benefits more strongly. This set claims to optimize engine fuel efficiency by 15%–20% and actively reduces common engine issues like lack of power and start-up failures. The coils use German-imported copper windings and high-temperature resistant epoxy resin, suggesting a focus on achieving stable high voltage output.

Key features that stand out:
– Optimized MPG: Designed to improve fuel efficiency and reduce carbon deposition significantly.
– High-Quality Coils: Utilizes premium materials like imported copper windings for stable, long-term high voltage.
– Long Plug Life: Iridium plugs are rated for a lifespan of up to 60,000–100,000 miles.

• Pros: Strong emphasis on performance boost and fuel economy improvement; high-quality material claims for the coil packs; eliminates ignition system guesswork.
• Cons: The claim of a 15-20% MPG increase is often unrealistic in real-world driving conditions.
• Best for: Those seeking a full, performance-oriented ignition overhaul for their 2004 Envoy.

Expert Opinion: When assessing combination kits, the coil quality is just as important as the plug material. The emphasis on high-purity copper windings suggests these coils are built to handle the heat generated by the continuous operation of the 4.2L L6 engine, providing long-term benefits beyond just the initial spark plug replacement.

Iridium Spark Plugs 6 Pack Compatible with Chevrolet Silverado 1500 Express 2500 3500 Trailblazer, GMC Envoy Sierra Savana, Buick Rainier, Isuzu Ascender, Saab 9-7x, Replaces 91418, ILTR5E11, 41-114

If you simply want robust iridium plugs built to high standards without the complexity of a coil kit, this 6-pack is a solid contender. It’s engineered specifically for durability, featuring an iridium alloy central electrode that is laser-welded for superior thermal and electrical wear resistance. This set offers excellent value for a high-quality, long-life spark plug that covers the entire 2002-2009 run of the GMC Envoy 4.2L.

Key features that stand out:
– Laser-Welded Iridium: Enhances durability and ensures a precise, long-lasting connection.
– Wide Compatibility: Fits many GM L6 and V6 engines, ensuring a well-tested design for the 4.2L.
– Common Reference Numbers: Replaces many popular OEM and aftermarket parts (91418, 41-114), simplifying selection.

• Pros: Durable iridium material; great resistance to thermal breakdown; reliable performance across the Envoy’s operating range.
• Cons: Does not include new coil boots or dielectric grease, requiring separate purchase.
• Best for: The everyday driver who needs a reliable, long-life iridium replacement without needing to change the coils yet.

Expert Opinion: The focus on iridium alloy diameter (0.4-0.6 millimeters) indicates a fine-tuning of the design to balance durability with spark efficiency. For the 2004 Envoy, this plug offers an excellent compromise between the high cost of OEM and the uncertainty of very generic aftermarket options.

ACDelco GM Original Equipment 41-962 (19299585) Double Platinum Spark Plug (Pack of 1)

When it comes to your 2004 GMC Envoy, nothing beats sticking to the factory standards set by General Motors. The ACDelco GM Original Equipment plugs are rigorously tested and designed specifically for your vehicle. These are double platinum plugs, meaning platinum is used on both the center and ground electrodes. This provides excellent durability, consistent voltage demands, and reduced wear on the ignition system, ensuring your Envoy runs exactly as GM intended.

Key features that stand out:
– Double Platinum: Platinum pads on both electrodes for maximum lifespan and consistent gap maintenance.
– OEM Specification: Designed, engineered, and tested to meet rigorous GM standards.
– Fouling Resistance: Pure copper core helps maintain cooler electrode temperature, maximizing durability and resisting deposits.

• Pros: Guarantees exact fit and function as per GM specifications; excellent durability and consistency; built-in suppressor seal reduces electronic interference.
• Cons: Sold individually (requiring purchase of 6); double platinum is generally less durable than iridium.
• Best for: Purists who demand strict adherence to Original Equipment Manufacturer (OEM) parts for guaranteed compatibility and reliability.

Expert Opinion: If you still have the original coils and just need new plugs, the ACDelco 41-962 is the safest bet. The integrated suppressor seal is a detail often overlooked in aftermarket options, but it’s critical for minimizing radio frequency interference and protecting sensitive on-board electronics.

Comparison and Short Insights

When comparing the options for your 2004 GMC Envoy spark plug replacement, the biggest choice is usually between material and complexity.

If pure longevity is your goal, stick with the Iridium options like the A-Premium or Iridium Spark Plugs 6 Pack. These plugs offer service intervals often exceeding 100,000 miles, far beyond traditional plugs.

For guaranteed reliability and system preservation, the ACDelco Double Platinum is the clear choice. You pay for the OEM pedigree, but you get a tested product designed specifically for the L6 4.2L.

The most cost-effective solution for a complete ignition tune-up are the coil and plug kits (Set of 6 Ignition Coil Pack or UF303 Ignition Coil Pack). While aftermarket coils can vary in quality, the value of replacing both items at once on an older vehicle is substantial. This is especially true if you are experiencing misfires or hesitation.

Finally, the NGK G-Power Platinum stands out as the best choice for those seeking a premium, reliable mid-range plug that avoids the cost of iridium but still delivers excellent anti-seizing properties and trusted brand performance.

Final Verdict: Our Top Recommendation for Your Envoy

Selecting the best spark plug depends entirely on your vehicle’s current needs and your budget for maintenance.

The Best All-Around Performer: We recommend the A-Premium Iridium Platinum Spark Plugs. They combine the durability of Iridium with the consistent spark of Platinum, offering the longest lifespan and best heat management for the 4.2L engine, making them a worthwhile investment that pays off over tens of thousands of miles.

The Safest OEM Bet: If you prefer factory-spec performance above all else, the ACDelco GM Original Equipment 41-962 Double Platinum plugs are the guaranteed choice for seamless compatibility and engine protection.

The Best Value Overhaul: If your Envoy has over 120,000 miles, consider the UF303 Ignition Coil Pack and Iridium Spark Plugs Set of 6. Replacing the entire system prevents future failures and immediately maximizes the performance benefits of the new iridium plugs.

Best Spark Plugs For 2004 GMC Envoy FAQ

Q1: What is the correct spark plug gap for the 2004 GMC Envoy 4.2L L6 engine?

A: The correct gap specification for the 2004 GMC Envoy 4.2L L6 engine is typically 0.040 inches (1.0 mm). While some manufacturers pre-gap iridium plugs to 0.044 inches or 0.050 inches due to their fine-wire design, it is always best practice to check and adjust the gap to the factory specification using a wire gauge for optimal performance and long life.

Q2: Should I choose Iridium or Platinum spark plugs for my 2004 GMC Envoy?

A: Iridium is generally superior in terms of longevity and performance. Iridium plugs have the longest lifespan (often 100,000+ miles) and provide a more focused, consistent spark. Platinum plugs (especially double platinum like the ACDelco OE part) are durable, too, but typically last around 60,000 to 80,000 miles. For a long-term investment in your 2004 GMC Envoy, iridium is recommended.

Q3: How often should I replace the spark plugs in my 4.2L Envoy?

A: The recommended service interval depends on the plug material. If you install OEM or good quality Platinum plugs, replacement should occur every 60,000 to 80,000 miles. If you opt for modern Iridium spark plugs, you can safely wait until 80,000 to 100,000 miles. Always consult your owner’s manual or check your vehicle’s performance for early signs of wear.

Q4: Do I need special tools to perform a 2004 GMC Envoy spark plug replacement?

A: Yes, replacing the 2004 GMC Envoy spark plugs requires a few specific tools beyond a standard socket set. You will need a 5/8-inch spark plug socket (which usually has a rubber insert to grip the plug), a long extension (due to the deep location of the plugs on the inline-six engine), and a torque wrench to ensure the new plugs are tightened to the correct specification to prevent damage to the cylinder head.

Q5: What are the symptoms of bad spark plugs in a GMC Envoy?

A: Common symptoms indicating that you need new spark plugs include rough idling, difficulty starting the vehicle, noticeable hesitation or misfires during acceleration, and a significant decrease in fuel economy. If the plugs are severely worn, the Check Engine Light (CEL) may illuminate, often indicating a specific cylinder misfire code.

Q6: Why do some kits include new ignition coils? Should I replace them too?

A: Some products, like the UF303 kits, include new ignition coils because the coils on the 4.2L L6 engine often fail around the same time as the spark plugs need replacement (especially after 100,000 miles). Replacing both at once ensures the entire ignition system is refreshed, solving potential performance issues stemming from either worn plugs or weak coils, providing peace of mind and optimizing the system’s output.