A Guide to Spark Plugs for the 2003-2010 Infiniti M45
Keep your M45's powerful VK45DE V8 engine running at its peak by choosing the right spark plugs.
- Stick with NGK or Denso Iridium or Platinum plugs for the best OEM-like performance and longevity on your M45.
- Symptoms like a rough idle, poor gas mileage, and hesitation are strong indicators that your spark plugs need inspection.
- While DIY replacement is possible, be prepared for a challenge reaching the rear cylinders near the firewall.
- Always verify the spark plug gap is correct (0.044") before installation, even if they are advertised as pre-gapped.
Signs of Failing Spark Plugs
When your spark plugs wear out, your M45 will let you know. The signs can start small but will worsen over time. Ignoring them can lead to more expensive problems, including damage to your catalytic converter.
- Rough Idle: The engine may shake or vibrate when you're stopped at a light.
- Engine Misfires: You might feel a hesitation, stumble, or jerking during acceleration. This can also trigger a flashing Check Engine Light.
- Reduced Power: Your M45 may feel sluggish and less responsive than usual.
- Worse Gas Mileage: Inefficient combustion means you'll be visiting the gas station more often.
- Hard Starting: The engine may take longer to crank and start, especially in cold weather.
- Check Engine Light: A steady or flashing Check Engine Light, often with codes like P0300 (random misfire) or P0301-P0308 (cylinder-specific misfires), is a common indicator.
Choosing the Right Aftermarket Spark Plugs
The original spark plugs for the Infiniti M45 were typically NGK platinum plugs. When shopping for aftermarket replacements, you have several good options. The choice often comes down to material, which affects performance and lifespan.
Brand & Material Tiers
Tier 1: OEM Quality (NGK & Denso)
These brands are often the original equipment manufacturers for Infiniti. Choosing their Iridium or Platinum plugs is the safest bet for factory-like performance and longevity.
- NGK: Widely considered the factory supplier for the M45. Their Laser Platinum (e.g., PLFR5A-11) and Iridium IX plugs are excellent choices that meet or exceed OEM specifications.
- Denso: Another top-tier Japanese brand known for quality. Their Iridium plugs are a popular upgrade for improved throttle response and efficiency, though some high-performance versions may have a shorter lifespan.
Tier 2: Reputable Aftermarket (Bosch & Champion)
These are well-known brands that offer quality plugs, often at a more competitive price. Their double iridium and platinum options are reliable choices for the M45.
- Bosch: Offers Double Iridium and Platinum plugs that are a good alternative to OEM. Some owners choose Bosch as a reliable replacement.
- Champion: Provides Iridium and Platinum options that offer good performance and value.
Tier 3: Budget-Friendly (Autolite)
Autolite offers more affordable options, including Iridium and Platinum plugs. While they can be a good choice for those on a tighter budget, their lifespan might not match that of the premium brands.
Cost & Material Comparison
| Material | Typical Price Range (Per Plug) | General Lifespan | Best For |
|---|---|---|---|
| Iridium | $8 - $22 | 80,000 - 120,000 miles | Longevity and performance |
| Platinum | $6 - $15 | 60,000 - 100,000 miles | A balance of performance and cost |
| Copper | $4 - $8 | 20,000 - 30,000 miles | Lowest cost, but requires frequent changes |
Known Issues, Recalls, and TSBs
Searches for recalls and Technical Service Bulletins (TSBs) related specifically to spark plugs on the 2003-2010 Infiniti M45 did not yield any results. However, several recalls were issued for this vehicle, including significant ones for Takata airbag inflators and an accelerator pedal sensor issue that could cause the engine to enter a fail-safe mode. While not directly related to the plugs themselves, these are important for any M45 owner to be aware of.
Frequently Asked Questions
How often should I change the spark plugs on my M45?
The factory recommendation for the original platinum plugs is around 100,000-105,000 miles. If you use high-quality aftermarket Iridium or Platinum plugs, you can expect a similar lifespan. However, if you notice any symptoms of failure, you should inspect them sooner.
Do I need to gap the new spark plugs?
Most high-quality plugs from brands like NGK and Denso come pre-gapped. However, it is always a best practice to double-check the gap with a feeler gauge before installation. The specified gap for the M45 is typically 0.044 inches (1.1mm). A plug could have been dropped or mishandled during shipping, altering the gap.
🎬 See if you should gap your new Infiniti spark plugs.Should I replace the ignition coils with the spark plugs?
Your M45 uses a coil-on-plug ignition system, meaning each spark plug has its own ignition coil. You do not need to replace the coils with the plugs unless a coil has failed. A failed coil will usually cause a persistent misfire on a single cylinder (e.g., code P0304 for cylinder 4).
Is replacing the spark plugs a DIY job?
Yes, it is a feasible DIY job for someone with moderate mechanical experience. However, the V8 engine is tight in the engine bay. The rearmost plugs (cylinders 7 and 8, near the firewall) can be difficult to access. You will need a good socket set with various extensions and a universal joint.
🎬 Follow this step-by-step guide to replacing your M45 spark plugs.Helpful Videos
Technical Specifications
OEM Part Numbers: 22401-5M015 22401-EW61C 22401-5M016 22401-5M014
Socket Size: 5/8 inch (16mm) Gap: 0.044 inches (1.1 mm) Engine: VK45DE V8 Quantity: 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.
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