Mazda 6 Spark Plugs: Intervals, Fitment & Warning Signs

On the Mazda 6, repeatedly removing coil boots to "just check" plugs genuinely risks a microscopic scratch modern ignition systems can't tolerate.

Illustration for editorial purposes

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OEM Part Number: confirm via engine code — aftermarket NGK 6283 / Bosch 0 242 135 529

Accuracy note: Covers the Mazda 6 (GJ 2012-) as listed in the UK aftermarket catalogues. Spark plugs are engine-specific — thread size (M12 vs M14), reach, heat range, electrode type (copper, platinum, iridium) and gap all change between engines in the same car, and the catalogue listings below cover every petrol engine in the generation without always saying which plug fits which. Match the plug to your engine code (on the V5C or the engine cover), fit a full set of the same type, and use the maker's gap and torque. Genuine numbers are shown only where a listing quotes one.

Petrol engines in this generation	2.0 150 HP; 2.5 (GJ5FP) 188 HP; diesel variants also listed
Spark plugs (aftermarket)	NGK 6283 (iridium, M12x1.25, 14 mm hex); NGK 1654 (iridium, M12x1.25, 14 mm hex); NGK 94124 (iridium, M12x1.25, 14 mm hex); Denso ZC20HPR11 (iridium centre, platinum earth, M12x1.25; OE P51R-18-110); Denso IXEH22TT (iridium TT, M12x1.25); Champion OE253 (iridium, 1.0 mm gap, M12x1.25, 14 mm hex); Bosch 0 242 135 529 (1.1 mm gap, M12x1.25, 14 mm hex)
Genuine (OE) numbers quoted	Denso ZC20HPR11 = P51R-18-110
Fitment notes	The SKYACTIV-G petrols take an M12x1.25 / 14 mm hex iridium plug with a 1.0 to 1.1 mm gap; M14x1.25 / 16 mm plugs such as NGK 3689 and Denso IT16TT are also listed, so confirm the engine before buying. Brisk 1708 quotes a 100,000 km interval.

A Genuinely Important, Counter-Intuitive Warning Worth Knowing — Mazda 6 Spark Plugs

This is genuinely worth knowing before repeatedly pulling plugs to "just check" them: every time a coil and boot is removed and reinstalled, there's a genuine risk of causing a microscopic scratch on the plug's porcelain insulator. On modern engines, this risk is considerably higher than on older cars — leaner fuel mixtures and wider plug gaps mean today's ignition systems require far higher voltage, meaning a tiny scratch that would once have gone unnoticed can now genuinely cause a misfire.

A genuinely real, documented fitment trap worth knowing about aftermarket ignition boots: one documented case on a related model saw aftermarket boots that were noticeably shorter than genuine OEM boots cause genuine misfires initially, mistakenly blamed on the new spark plugs themselves.

It's also worth knowing a genuinely useful diagnostic distinction: finding oil specifically on the threads of a newly fitted spark plug points toward a valve cover gasket or seal leak, rather than a fault with the plug or coil itself.

Mazda 6 Spark Plugs: A Cheap Part That Causes Expensive-Feeling Problems

A worn set of spark plugs in the Mazda 6 doesn't make itself obvious: idle roughens slightly, acceleration loses a bit of urgency, and both symptoms are easy to blame on something else entirely. Given how inexpensive the part is, it often gets neglected for far longer than it should.

Mazda 6 Spark Plugs: Watch: Replacing It

🎬 Watch: How To Replace Spark Plugs 2014-2017 Mazda 6 2.5

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GJ generation, 2.5 petrol.

Before you buy: plug type and gap specification vary by engine size and generation. Always confirm against your VIN before ordering.

Mazda 6 Spark Plugs: What They Do

Every combustion cycle in the Mazda 6's petrol engine starts with a spark plug igniting the compressed fuel-air mixture, and their condition shapes efficiency, economy and smoothness directly. Diesel versions don't need them at all, relying purely on compression to ignite fuel.

Mazda 6 Spark Plugs: Generations & Spark Plug Count

Diesel variants, where fitted	Not applicable — diesel engines use compression ignition and have no spark plugs at all
Petrol variants (all trims)	4 spark plugs — one per cylinder

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Mazda 6 Spark Plugs: Warning Signs, DIY Difficulty & Aftermarket Advice

These are the same regardless of make or model — see our full Spark Plugs Guide for symptoms of worn plugs, why matching your exact plug specification matters, and trusted brands to buy from.

More Mazda Spark Plugs

The same part, covered across other Mazda models.