A Guide to Aftermarket Spark Plugs for the 2005-2007 Saturn Relay
Keep your Relay's V6 engine running strong by choosing the right spark plugs for a complete tune-up.
- Accessing the rear three spark plugs on the Saturn Relay V6 is very difficult and may require tilting the engine forward, making this a challenging DIY job.
- Iridium spark plugs from brands like NGK or Denso offer the best longevity and performance for the cost.
- Always check the spark plug gap before installation, even if the plugs are advertised as pre-gapped. The correct gap for the 3.9L V6 is 0.040 inches.
- If you find oil in the spark plug well, it could be a sign of a more serious engine issue described in a GM Technical Service Bulletin.
Signs of Failing Spark Plugs in Your Relay
Worn-out spark plugs can cause several noticeable problems. As the electrodes wear down from repeated use, the gap the spark must jump becomes wider, requiring more energy. Eventually, this can lead to a weak spark or no spark at all. You might experience a rough idle, difficulty starting the engine, slower acceleration, and worse gas mileage. If the check engine light comes on, codes for engine misfires (P0300, P0301-P0306) often point to failing spark plugs.
Known Issue: Oil or Coolant Fouling
A GM Technical Service Bulletin (TSB) notes that on some similar engines, oil or coolant can leak into the spark plug tubes. This is caused by porosity in the cylinder head and is a major repair. If you find oil on your spark plug's porcelain insulator when changing it, this could be the cause. This leak will foul the new plug and cause persistent misfires.
Choosing the Right Aftermarket Spark Plugs
For the 2005-2007 Saturn Relay, several types of aftermarket spark plugs are available. The original equipment manufacturer (OEM) for many GM vehicles is ACDelco, but brands like NGK and Denso are considered top-tier replacements by many technicians 🎬 Watch this review of the best spark plugs for 2025 and enthusiasts. Autolite and Champion offer reliable, budget-friendly options.
Brand & Material Tiers
- Premium (Best Performance & Longevity): Iridium plugs from NGK, Denso, and Bosch are your best bet for long life and consistent performance. They have a very hard electrode material that resists wear for up to 100,000 miles and provides a strong, efficient spark.
- Mid-Grade (Good Value & Durability): Double Platinum plugs from these same brands are a solid choice. They have platinum on both the center and ground electrodes, offering a longer service life than standard platinum or copper plugs. Autolite's XP Iridium line also falls into this category, offering advanced technology at a competitive price.
- Standard (Budget-Friendly): Copper plugs from brands like Champion are the most affordable but have the shortest lifespan. They are perfectly functional but will need to be changed more frequently, typically every 30,000 miles.
A Note on Spark Plug Gap
The spark plug gap is the distance between the center and ground electrodes. It's critical for proper engine performance. For the 3.9L V6 engine in the 2006-2007 Relay, the specified gap is 0.040 inches (1.00 mm). The 2005 Relay with the 3.5L V6 may use a different gap, often around 0.060 inches. While many iridium and platinum plugs come pre-gapped, it is crucial to verify the gap with a feeler gauge and adjust if necessary before installation.
Aftermarket Spark Plug Cost for Saturn Relay
| Plug Type | Brand Tier | Typical Price (per plug) | Estimated Lifespan |
|---|---|---|---|
| Iridium | NGK, Denso, Bosch | $10 - $21 | 80,000 - 100,000 miles |
| Double Platinum | Bosch, Autolite, NGK | $7 - $15 | 60,000 - 80,000 miles |
| Platinum | Champion, Autolite | $5 - $10 | 50,000 - 60,000 miles |
| Copper | Champion | $4 - $7 | ~30,000 miles |
Frequently Asked Questions
How often should I change the spark plugs on my Saturn Relay?
It depends on the type of plug. Iridium plugs can last up to 100,000 miles, while basic copper plugs should be changed around every 30,000 miles. Check your owner's manual for the recommended service interval, but if you are experiencing symptoms of failure, it's time for a change regardless of mileage.
Is it difficult to change the spark plugs on a Saturn Relay?
The difficulty is moderate. The front three spark plugs (on the cylinder bank near the radiator) are easy to access. However, the rear three plugs are located under the intake manifold against the firewall and are very difficult to reach. Many mechanics find it necessary to rotate the engine forward on its mounts to create enough space to access the rear plugs. This makes the job significantly more complex for a DIYer.
🎬 See a step-by-step guide on replacing Saturn spark plugsShould I replace the ignition coils and wires with the spark plugs?
The Saturn Relay uses a coil-on-plug ignition system, so it does not have traditional spark plug wires. While you don't need to replace the ignition coils with every spark plug change, it's a good time to inspect them. If a coil boot is cracked, oily, or shows signs of arcing (carbon tracking), it should be replaced. It is common practice to replace a coil if it is causing a specific cylinder's misfire code.
🎬 Learn how to locate specific cylinders on your GM engineWhat is the difference between Iridium and Platinum spark plugs?
Iridium is a harder, more durable metal than platinum. This allows manufacturers to make the center electrode very fine, which creates a more focused and efficient spark. This results in better performance and a longer lifespan compared to platinum plugs.
Helpful Videos
Technical Specifications
OEM Part Numbers: ACDelco 41-962 ACDelco 41-101
The 2005 Saturn Relay used a 3.5L V6 (LX9) engine. The 2006-2007 models used a 3.9L V6 (LZ9) engine. The 3.9L engine specifies a spark plug gap of 1.00 mm (0.040 in). The 3.5L engine often specifies a larger gap, around 0.060 in. Both are 60-degree pushrod V6 engines.
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The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
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