Infiniti Q45 Spark Plug Guide: Choosing the Right Plugs for 1990-2006 Models
Your Q45's V8 engine has very specific spark plug needs; here's how to get it right.
- You must match the spark plug material to your Q45's generation: Platinum for 1990-2001 and Iridium for 2002-2006.
- Stick with the OEM supplier brands, NGK and Denso, for the best reliability and to avoid performance issues.
- When replacing plugs, always inspect the spark plug wells for oil, which indicates a common valve cover gasket leak that must be fixed.
- Modern NGK and Denso plugs come pre-gapped; do not try to adjust them, especially iridium plugs.
Understanding Your Q45’s Specific Spark Plug Needs
Choosing the right spark plug for your Infiniti Q45 is more critical than for many other vehicles. The entire 1990-2006 production run used advanced V8 engines with specific ignition requirements. Using the wrong type of plug is a common mistake that leads to misfires, poor performance, and check engine lights. The most important factor is matching the spark plug to your Q45's generation.
Generation-Specific Requirements
- First Generation (1990-1996, G50): These models use the VH45DE V8 engine. The original factory plugs were platinum types, like the NGK PFR5B-11 or PFR6B-11. You should stick with a high-quality platinum plug from an OEM-equivalent brand for proven reliability.
- Second Generation (1997-2001, FGY33): Equipped with the VH41DE V8, this generation also requires platinum spark plugs. The recommended OEM part is typically the NGK PFR5G-11. Owners report that using other types can cause performance issues.
- Third Generation (2002-2006, F50): These Q45s have the modern VK45DE V8, which came from the factory with long-life iridium spark plugs. The ignition system is designed specifically for iridium plugs. Using a lower-grade platinum or copper plug will lead to a very short service life, misfires, and poor fuel economy.
Known Issue: Oil in Spark Plug Tubes
A very common problem on all generations of the Q45 is oil leaking from the valve cover gaskets into the spark plug tubes. This oil will soak the bottom of the ignition coil boot and foul the spark plug, causing a misfire (often a P0300-P0308 code). 🎬 Watch: Troubleshooting multiple misfire codes on a second generation Q45. When you pull the ignition coils out, inspect the tubes for any signs of liquid oil. If oil is present, you must replace the valve cover gaskets to fix the root cause.
🎬 See how to fix oil leaks in your spark plug tubes.Choosing the Right Aftermarket Spark Plug
While many brands are available, Q45 owners have found that these engines are sensitive to plug choice. Sticking close to the original equipment design is the best path to success.
Brand Tiers for the Infiniti Q45
- Top Tier (OEM Equivalent): NGK and Denso were the original equipment suppliers for Infiniti. They are the most trusted and consistently recommended brands by long-time Q45 owners. Choosing the correct platinum or iridium plug from NGK or Denso is the safest and most reliable option.
- Mid-Grade (Use with Caution): Brands like Autolite and Champion offer platinum and iridium plugs that may fit, but they lack the proven track record of NGK and Denso in these specific engines. They are a potential budget option, but carry a higher risk of subtle performance issues.
- Avoid: Forum discussions among Q45 owners strongly warn against using Bosch spark plugs, especially the multi-electrode designs. Owners have reported running issues after installing them. Basic copper plugs should also be avoided entirely, as they are not compatible with the Q45's ignition system and will wear out extremely quickly.
A Note on Gapping
Modern platinum and iridium spark plugs from NGK and Denso come pre-gapped from the factory for your specific vehicle. While you can verify the gap with a feeler gauge, you should not attempt to adjust it, as you can easily break the fine, brittle electrode tip. The factory service manual even states that checking or regapping is not necessary.
Aftermarket Spark Plug Cost for 1990-2006 Infiniti Q45
| Category | Price Range (Set of 8) | Notes |
|---|---|---|
| Budget Aftermarket (e.g., basic Platinum) | $40 - $80 | Ensure they are the correct material (Platinum/Iridium). Quality may not match top-tier brands. |
| Premium Aftermarket (e.g., NGK/Denso Platinum) | $80 - $120 | Recommended for 1990-2001 models. Offers OEM performance and longevity. |
| Premium Aftermarket (e.g., NGK/Denso Iridium) | $100 - $170 | Required for 2002-2006 models. Offers the best performance and longest life. |
| OEM (from dealership) | $110 - $220 | The highest cost option, these are typically just rebranded NGK or Denso plugs. |
Frequently Asked Questions (FAQ)
How often should I change my Q45's spark plugs?
For 1990-2001 models with platinum plugs, the typical replacement interval is every 60,000 miles. For 2002-2006 models with iridium plugs, the interval is up to 100,000 miles. However, if you experience any failure symptoms, you should inspect and replace them sooner.
Can I use cheaper platinum plugs in my 2004 Q45 that requires iridium?
This is not recommended. The ignition system on the 2002-2006 Q45's VK45DE engine is designed for the specific electrical and heat characteristics of iridium plugs. Using a lower-grade plug can cause misfires, poor fuel economy, and will wear out much faster, forcing you to do the job again much sooner.
What is a spark plug's "heat range" and why does it matter?
Heat range is a measure of the spark plug's ability to dissipate heat from the firing tip. A "hotter" plug retains more heat, while a "colder" plug transfers more heat away. For a stock Q45 engine, you must use the stock heat range recommended by the manufacturer. Using a plug that is too hot can lead to pre-ignition (detonation), and a plug that is too cold can lead to carbon fouling. Colder plugs are only necessary for engines with significant power modifications, like a turbocharger.
Is it difficult to change the spark plugs on a Q45 myself?
The process is straightforward, but access can be tight. It involves removing the engine cover and ignition coils. The rearmost plugs on the V8 are the most difficult to reach. You will need a spark plug socket, a few different lengths of extensions, and patience. It is a manageable DIY job for someone with basic mechanical experience.
🎬 Watch: A step-by-step walkthrough for changing plugs on the F50 generation.Helpful Videos
Technical Specifications
OEM Part Numbers: 22401-1P115 (PFR5G-11) 22401-1P116 (PFR6B-11) 22401-1P114 22401-5M015
Socket Size: 5/8 in. (16mm) Plug Material by Year: - 1990-2001: Platinum - 2002-2006: Iridium Number of Plugs: 8
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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.
- Infiniti Q45:
- 🎬 Helpful Videos
- 🛍️ Shop This Part
- Understanding Your Q45’s Specific Spark Plug Needs
- Generation-Specific Requirements
- Known Issue: Oil in Spark Plug Tubes
- Choosing the Right Aftermarket Spark Plug
- Brand Tiers for the Infiniti Q45
- A Note on Gapping
- Aftermarket Spark Plug Cost for 1990-2006 Infiniti Q45
- Frequently Asked Questions (FAQ)
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