A Guide to Spark Plug Replacement for the 2015-2021 Mazda 6
Keep your Mazda 6 running smoothly by choosing the right spark plugs for your Skyactiv engine.
- Use NGK or Denso Iridium spark plugs; NGK is the OEM manufacturer and offers the same quality as Mazda-branded parts for less money.
- The replacement interval is 75,000 miles for the 2.5L non-turbo engine and only 40,000 miles for the 2.5T turbo engine.
- This is a DIY-friendly job, but you must use a special 14mm (9/16") thin-wall spark plug socket.
- Avoid using Bosch plugs if possible, as many owners and technicians report issues with them in Japanese engines.
Signs of Failing Spark Plugs in Your Mazda 6
Worn-out spark plugs can cause noticeable problems with your car's performance. If your Mazda 6 is experiencing any of these issues, it might be time for a new set of plugs:
- Rough Idle: The engine may shake or vibrate more than usual when you're stopped.
- Engine Misfires: You might feel a hesitation or stumble from the engine during acceleration. This can also trigger the Check Engine Light with codes like P0300, P0301, P0302, P0303, or P0304.
- Reduced Fuel Economy: Worn plugs can cause inefficient fuel burn, making you visit the gas station more often.
- Poor Acceleration: The car may feel sluggish or less responsive when you press the gas pedal.
- Difficulty Starting: An engine that cranks for a long time before starting can be a sign of weak spark.
OEM vs. Aftermarket Spark Plugs
When shopping for spark plugs for your Mazda 6, you'll find Mazda-branded "OEM" parts and aftermarket options. For this specific vehicle, the choice is straightforward.
Mazda does not manufacture its own spark plugs; they are made by NGK. The NGK-branded aftermarket plug is often the exact same part as the one you'd buy in a Mazda box, just at a lower price. Owner and technician communities overwhelmingly agree that using the OEM-equivalent NGK plugs is the best choice for reliability and performance. Denso is another highly-regarded Japanese brand that makes excellent quality plugs and is a safe alternative.
A Note on Engine Type and Service Intervals
The 2015-2021 Mazda 6 came with two different 2.5L engines, and their spark plug replacement schedules are very different. Always confirm which engine you have.
- 2.5L Skyactiv-G (Naturally Aspirated): Replace every 75,000 miles.
- 2.5T Skyactiv-G (Turbo): Replace every 40,000 miles.
The shorter interval on the turbo engine is due to the higher combustion pressures and heat it generates, which wears out the plugs faster.
🎬 See this replacement walkthrough for the 2.5 Turbo engine.Choosing the Right Aftermarket Brand
Not all spark plugs are created equal. For your Mazda 6's sensitive Skyactiv engine, sticking with proven brands is recommended.
- Top Tier (Recommended): NGK is the original equipment manufacturer and the most recommended brand by far. Their Laser Iridium plugs are designed for long life and performance in your engine. Denso is also a top-quality choice with a strong reputation.
- Mid Tier (Use with Caution): Bosch Double Iridium plugs are available and some owners use them without issue. However, many professional mechanics and owners on forums report that Bosch plugs can sometimes cause running issues in Japanese vehicles.
- Economy Tier (Generally Not Recommended): While Champion is a well-known brand, there is very little information about their use in this specific Mazda 6 generation. Given that the price difference is often small, it is safer to stick with the proven OEM equivalent from NGK or Denso.
| Part Type | Estimated Cost |
|---|---|
| New OEM (Mazda Branded) | $120 - $175 |
| New Aftermarket (NGK/Denso) | $32 - $120 |
| Shop Labor | $100 - $150 |
DIY Installation Tip
Replacing the spark plugs on a Mazda 6 is a relatively easy DIY job. However, you will need a specific 14mm (or 9/16") thin-wall spark plug socket, as a standard socket will not fit into the engine head. Always tighten the new plugs with a torque wrench to the specified value, which is typically 12-14 ft-lbs.
🎬 Watch: Step-by-step guide to changing your Skyactiv engine spark plugs.Frequently Asked Questions
Do I have to buy the expensive Mazda-branded spark plugs?
No. The Mazda plugs are made by NGK. You can buy the identical NGK Laser Iridium plug for less money, and it will perform exactly the same.
Are there any recalls or TSBs for Mazda 6 spark plugs?
No. Searches of the NHTSA database and technical service bulletins show no specific recalls or service actions for spark plug issues on the 2015-2021 Mazda 6.
Why is the replacement interval so much shorter on the turbo engine?
The 2.5T engine creates more heat and pressure in the cylinders. This environment is harder on the spark plugs, causing the electrodes to wear down faster. Sticking to the 40,000-mile interval is critical for the health and performance of the turbo engine.
Do I need to gap the new spark plugs?
Most high-quality Iridium plugs from NGK or Denso come pre-gapped from the factory. It is always a good practice to verify the gap with a feeler gauge before installation, but you should not need to adjust them. Attempting to gap a fine-wire iridium plug can easily damage the delicate electrode.
Helpful Videos
Technical Specifications
OEM Part Numbers: PE5R-18-110 PE5R-18-110A PY8V-18-110
Socket Size: 14mm or 9/16" thin-wall. Torque: 12-14 ft-lbs. OEM Material: Iridium. Engine Fitment: 2.5L Skyactiv-G (PE5R-18-110) or 2.5T Skyactiv-G (PY8V-18-110).
We Have This Part in Stock
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.
- Mazda 6: