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DIY spark plug replacement on 2017 Mazda3 2.5L?

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Mike T. · rep 0 · May 22, 4:52 AM · 1 replies · solved · Question

Vehicle: 2017 Mazda3 Grand Touring

Hi all, I'm looking to replace the spark plugs on my 2017 Mazda3 Grand Touring with the 2.5L engine. It's got about 85,000 miles on it now, and I figure it's probably time. The car runs fine, no misfires or anything, but I want to keep up with maintenance.

Has anyone done this DIY? Is it pretty straightforward, or are there any tricky parts I should be aware of? What kind of plugs should I get? I'm comfortable with basic wrenching, but I don't want to get into something over my head. Any tips or specific tools needed would be super helpful!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:52 AM

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ClearTheCode admin answer:

Replacing spark plugs on your 2017 Mazda3 with the 2.5L Skyactiv-G engine is a very manageable DIY project for someone with basic mechanical skills. Mazda generally recommends spark plug replacement around 75,000 miles for these engines, so you're right on schedule.

Here's a breakdown to help you:

  1. Tools and Parts Needed:

    • New Spark Plugs: You'll need NGK Laser Iridium plugs, specifically PE5R-18-110 (or NGK part number DILKAR7L11). These are OEM and highly recommended.
    • Spark Plug Socket (usually 14mm thin-wall, 6-point with a rubber insert to hold the plug).
    • Ratchet and various extensions.
    • Torque Wrench (essential for proper installation).
    • Dielectric grease (for coil pack boots).
    • Anti-seize compound (optional, but recommended for threads).
    • Flathead screwdriver or trim removal tool (for plastic covers).

  2. Procedure Overview:

    • Preparation: Ensure the engine is cool. Disconnect the negative terminal of the battery for safety (optional but good practice). Remove the engine cover.
    • Access Coils: Disconnect the electrical connectors from each ignition coil pack. Then, unbolt and carefully pull each coil pack straight up and out.
    • Remove Old Plugs: Using your spark plug socket and extension, carefully loosen and remove each old spark plug. Inspect them for wear, which can give clues about engine health.
    • Install New Plugs: Apply a small amount of anti-seize to the threads of the new plugs (avoiding the electrode). Hand-thread each new plug into the cylinder head to prevent cross-threading. Once finger-tight, use your torque wrench to tighten them to the manufacturer's specification (typically around 10-13 ft-lbs for these plugs).
    • Reassembly: Apply a small amount of dielectric grease inside the coil pack boots. Reinstall the coil packs, ensuring they seat properly over the plugs. Reconnect electrical connectors and replace the engine cover.

  3. Common Pitfalls & Tips:

    • Cross-threading: This is the biggest risk. Always start plugs by hand. If it feels like it's binding, stop and re-thread.
    • Over-tightening: Can strip threads or damage the plug. Use a torque wrench.
    • Dropping Plugs: Never drop a new spark plug, as it can damage the electrode or ceramic insulator.

If you encounter any difficulty or are unsure at any point, it's always best to consult a professional mechanic. However, with patience and the right tools, this is a very rewarding DIY.

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