Infiniti FX50 Spark Plug Replacement Guide (2009-2013)
Everything you need to know about choosing the right spark plugs for your FX50's V8 engine.
- Only use high-quality Iridium spark plugs from brands like NGK or Denso to match OEM performance.
- The replacement job is difficult and time-consuming (2-3 hours), so it's wise to invest in the best possible plugs.
- While changing the plugs, inspect the spark plug wells for oil, which indicates a failing valve cover gasket that must be replaced.
- The factory-recommended replacement interval is 105,000 miles, but symptoms can appear sooner.
Symptoms of Failing Spark Plugs
When your FX50's spark plugs begin to fail, you will notice clear signs related to engine performance. Because these parts are so critical to the combustion process, symptoms are usually obvious. Ignoring them can lead to more expensive repairs down the road.
- Engine Misfires and Rough Idle: This is the most common symptom. You may feel the engine sputter, shake, or hesitate, especially when stopped or during acceleration. This will often trigger the Check Engine Light with codes from P0300 to P0308. 🎬 Watch: How to diagnose and repair a cylinder misfire code
- Reduced Fuel Economy: Worn plugs are less efficient, causing incomplete fuel combustion. This can decrease your gas mileage by as much as 30%.
- Poor Acceleration: If your FX50 feels sluggish or less powerful than it used to, failing spark plugs are a likely cause. A weak spark robs the engine of its power.
- Difficulty Starting: The engine might take longer to crank before it starts up.
A Common Related Issue: Oil in Spark Plug Wells
Many FX50 owners report finding engine oil on the ignition coils and spark plugs during a change. This is not caused by the spark plugs themselves but by a failing valve cover gasket or spark plug tube seals. If you see oil, it is critical to replace these gaskets to prevent the new plugs and ignition coils from being damaged.
🎬 See this walkthrough on replacing your valve cover gasketsChoosing the Right Aftermarket Spark Plugs
The Infiniti FX50's VK50VE engine was designed for high performance, and it requires high-quality spark plugs to match. The original factory plugs are long-life iridium types, and you should only use iridium replacements to maintain performance and longevity.
OEM vs. Aftermarket Quality
For this vehicle, the Original Equipment Manufacturer (OEM) plugs were made by Denso. Top-tier aftermarket brands like NGK and Denso offer plugs that are equivalent or even identical to the original parts. Cheaper platinum or copper plugs are not recommended for the FX50 engine.
- Top Tier (OEM-Equivalent): NGK and Denso are the preferred brands for most Japanese vehicles, including Infiniti. Their Laser Iridium (NGK) and Long-Life Iridium (Denso) plugs are designed to meet or exceed factory specifications and offer a service life of up to 105,000 miles. You can't go wrong with these choices.
- Mid-Tier (Quality Alternative): Bosch Double Iridium plugs are a strong and reliable alternative. They offer similar longevity and performance to NGK and Denso, making them a perfectly suitable choice if you find a good deal.
- Economy Tier (Not Recommended): While brands like Champion do make spark plugs that fit, they are generally considered a step down in quality for this specific high-output engine. Given the extreme difficulty of the installation, saving a few dollars on the plugs themselves is not worth the risk of reduced performance or a shorter lifespan.
| Brand | Tier | Typical Price (per plug) | Notes |
|---|---|---|---|
| NGK | Top Tier | $15 - $29 | Often considered the gold standard for Japanese engines. Excellent performance and longevity. |
| Denso | Top Tier (OEM) | $19 - $25 | The original manufacturer for the FX50. Guaranteed compatibility and performance. |
| Bosch | Mid-Tier | $9 - $20 | A high-quality German brand offering comparable iridium plugs. A solid choice. |
| Champion | Economy | $8 - $15 | Functional, but not the best match for this engine's demands. |
Installation is Difficult
Replacing the spark plugs on the FX50's 5.0L V8 is a time-consuming and challenging job, even for experienced mechanics. It can take 2-3 hours and requires removing the engine cover and dual air intake assemblies to access the ignition coils. The rearmost plugs are especially difficult to reach. You will need a specific 14mm swivel spark plug socket, multiple extensions, and possibly a magnetic retrieval tool. Due to the high labor cost, it is wise to invest in high-quality plugs so you don't have to do the job again for another 100,000 miles.
🎬 Watch a complete spark plug replacement on the FX50 V8Frequently Asked Questions (FAQ)
When should I replace the spark plugs on my 2009-2013 FX50?
The manufacturer's recommended replacement interval for the original iridium spark plugs is 105,000 miles. However, if you experience any failure symptoms like misfiring or a drop in fuel economy, you should have them inspected immediately, regardless of mileage.
What is the correct spark plug gap for the FX50?
The correct spark plug gap is 0.044 inches (1.1mm). High-quality iridium plugs from NGK, Denso, and Bosch typically come pre-gapped and should not be adjusted, as you risk damaging the fine iridium tip.
Do I need to reset the computer (ECU) after changing the spark plugs?
Some owners report that the engine runs rough immediately after a spark plug change. This can happen because the engine's computer has adapted over time to the performance of the old, worn plugs. Performing an ECU reset (by disconnecting the battery for about 30 minutes) will force the computer to relearn with the new plugs, which usually resolves the issue.
Are there any recalls for the FX50 spark plugs?
No. As of early 2026, there are no specific recalls or Technical Service Bulletins (TSBs) from the NHTSA that relate directly to the spark plugs on the 2009-2013 Infiniti FX50.
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Technical Specifications
OEM Part Numbers: 22401-EW61C 22401-JK01D
The original equipment plug is a Denso Iridium plug (FXE22HR11) with a required gap of 0.044 inches (1.1mm). A 14mm spark plug socket is required for installation.
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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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