A Guide to Spark Plugs for the 2006-2010 Infiniti M35
Keep your M35's V6 engine running smoothly with the right set of new spark plugs.
- Stick to OEM brands NGK or Denso for spark plugs to ensure compatibility and avoid potential issues with the M35's engine.
- Symptoms like rough idle and poor acceleration are strong indicators, but a hard start could also point to failing crank/cam sensors.
- Replacement is a manageable DIY task that takes about two hours, but accessing the driver's side plugs requires patience and the right tools.
- Always use long-life Iridium or Platinum plugs to match the factory-recommended 100,000-mile service interval.
Symptoms of Failing Spark Plugs
When your M35's spark plugs start to wear out, your car will give you several warning signs. Worn electrodes or carbon buildup can weaken the spark, leading to incomplete combustion. You will likely notice one or more of the following issues:
- Rough Idle: The engine may shake or vibrate more than usual when stopped.
- Engine Misfires: You might feel a hesitation or stumbling during acceleration. This will often trigger the Check Engine Light with codes from P0300 to P0306. 🎬 Watch how a real-world misfire was diagnosed and fixed.
- Reduced Fuel Economy: Inefficient combustion means you'll be visiting the gas station more often. A bad plug can reduce fuel economy by up to 30%.
- Poor Acceleration: The car may feel sluggish or slow to respond when you press the gas pedal.
- Difficulty Starting: Worn plugs can make it harder for the engine to turn over, especially in cold weather.
A Note on Other Sensors
Some symptoms, like a long crank time before the engine starts, can also be caused by failing camshaft or crankshaft position sensors, a known issue on the VQ35DE engine. If you replace your spark plugs and still have starting issues, these sensors may be the next logical part to inspect.
Choosing the Right Aftermarket Spark Plugs
For the 2006-2010 Infiniti M35, choosing the right brand is more important than simply finding a plug that fits. The VQ35DE engine is known to be sensitive to spark plug brands. Owner and mechanic communities overwhelmingly recommend sticking with the Original Equipment (OEM) brands, NGK and Denso.
Brand Quality Tiers
- Best (OEM-Equivalent): NGK & Denso
These are the brands Infiniti used when building your car. Choosing their Iridium or Platinum plugs is the safest bet for performance and longevity that matches the original parts. They are engineered specifically for Nissan and Infiniti engines and have a proven track record of reliability. Many forum users warn against using other brands, even reputable ones like Bosch, due to stories of premature failure in these specific engines. - Good (Budget-Friendly): Autolite & Champion
Brands like Autolite and Champion offer Iridium and Platinum plugs that will fit your M35, often at a lower price point. While they are a viable option, they are not the factory-specified choice. If you opt for a standard copper plug from these brands, be aware that its service life will be much shorter (around 30,000 miles) than the 100,000-mile interval of the original iridium plugs. - Use with Caution: Bosch
While Bosch is a major manufacturer of quality auto parts, numerous Infiniti owners have reported issues when using their spark plugs in VQ-series engines. To avoid potential problems, it is generally recommended to stick with NGK or Denso.
Iridium vs. Platinum Plugs
The original spark plugs in your M35 are long-life plugs, typically platinum or iridium. Iridium is a harder, more durable material than platinum, with a higher melting point. This allows for a very fine center electrode, which requires less voltage to create a spark, offering excellent durability and a consistently stable spark. Both NGK Laser Platinum and Iridium IX plugs are excellent choices for this vehicle.
Cost to Replace Infiniti M35 Spark Plugs
| Category | Estimated Cost |
|---|---|
| Shop Labor | $171 - $251 |
| New Aftermarket Plugs (Set of 6) | $25 - $177 |
| New OEM Plugs (Set of 6) | $84 - $140 |
| Total Professional Replacement | $255 - $390 |
Frequently Asked Questions
How often should I replace the spark plugs on my M35?
If you use OEM-quality iridium or platinum spark plugs, the recommended replacement interval is typically every 100,000 miles. Some owners choose to replace them earlier, around 70,000-80,000 miles, as preventative maintenance. If you use basic copper plugs, you will need to change them much more frequently, around every 30,000 miles.
Is replacing the spark plugs a DIY job?
Yes, this is a job that many owners do themselves. However, it can be tricky. It requires removing the engine cover and some air intake components to access the ignition coils. The three plugs on the driver's side are more difficult to reach than the passenger's side due to tighter space. You will need a 10mm socket, a 5/8-inch thin-wall spark plug socket, and various extensions. 🎬 Watch: How to replace your spark plugs and ignition coils. It took one experienced owner about two hours while being careful.
🎬 See this step-by-step spark plug replacement walkthrough.Do I need to gap the new spark plugs?
Most high-quality iridium and platinum plugs from NGK and Denso come pre-gapped and should not be adjusted. The fine-wire tips are fragile and can be damaged easily. It's always a good idea to double-check the gap with a feeler gauge, but be extremely gentle if you do.
Are there any recalls for the M35 spark plugs?
No, there are no recalls or technical service bulletins (TSBs) from Infiniti specifically related to spark plugs for the 2006-2010 M35. Recalls for this vehicle primarily concern Takata airbags and an accelerator pedal sensor.
Helpful Videos
Technical Specifications
OEM Part Numbers: PLFR5A-11
Socket Size: 5/8 inch Thread Diameter: 14mm Recommended Brands: NGK, Denso Recommended Material: Iridium or Platinum Quantity Required: 6
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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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