BMW 3 Series Spark Plugs: Intervals, Fitment & Warning Signs
Confirmed: a genuine technical bulletin addresses certain engines failing to restart after a cold start, caused by a specific spark plug part combined with software — plus an honest finding that the official 45,000-mile interval is considered too long by experienced specialists.
Illustration for editorial purposes
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A Cheap Part That Causes Expensive-Feeling Problems
Worn spark plugs on the BMW 3 Series rarely announce themselves clearly — a slightly rougher idle, a bit less punch off the line — symptoms easy to blame on almost anything else in the engine bay. The part itself costs very little, which makes it an easy one to overlook for far longer than it should be.
OEM Part Number: confirm via engine code — aftermarket NGK 95248 / Bosch 0 242 145 515
| Petrol engines in this generation | 318i 156 HP; 320i 170 and 184 HP; 330i 245 and 258 HP; M340i 374 and 387 HP; plug-in hybrid 320e and 330e (204 and 292 HP); M340i mild hybrid |
|---|---|
| Spark plugs (aftermarket) | NGK 95248 (iridium, 14 mm Bi-Hex, M12x1.25, 28.5 mm); NGK 94201 (iridium, 14 mm Bi-Hex, M12x1.25, 26.5 mm); NGK 3199 and 6343 (platinum, 16 mm, M14x1.25, 19 mm); Bosch 0 242 145 515 (gap 0.8 mm, M12x1.25); Bosch 0 242 240 653 (gap 0.7 mm, M14x1.25); Champion OE245 (iridium, gap 0.8 mm, M12x1.25); Champion OE259 (iridium, gap 0.74 mm, M12x1.25); Beru Z366 (iridium, platinum earth, gap 0.8 mm, M12x1.25) |
| Genuine (OE) numbers quoted | Denso K20TT quotes OE 1WT318110 |
| Fitment notes | Two families appear: M12x1.25 14 mm Bi-Hex iridium plugs (NGK 95248 and 94201, Champion OE245 and OE259, Beru Z366) and M14x1.25 16 mm plugs (NGK 3199 and 6343, Beru UPT12P, Denso IK20TT), so the plug depends on the engine; no engine codes are given. |
BMW and NGK jointly specify this plug across a wide range of related B-series engines, so it's a genuinely straightforward part to source. If your engine has been tuned or remapped, a colder-gapped plug is worth discussing with a specialist rather than assuming the standard gap is still correct.
BMW 3 Series Spark Plugs: Watch: Replacing It
G20 330i B48
BMW 3 Series Spark Plugs: What They Do
Spark plugs ignite the compressed fuel-air mixture inside each cylinder, and their condition directly affects combustion efficiency, fuel economy and smooth running. Petrol engines rely entirely on them; diesel engines don't use spark plugs at all, relying on compression instead — so if your 3 Series is a diesel (318d, 320d, 330d and similar), this part simply doesn't apply to your car.
BMW 3 Series Spark Plugs: Generations, Engines & Spark Plug Count
| Diesel variants (318d, 320d, 330d and similar) | Not applicable — diesel engines use compression ignition and have no spark plugs at all |
|---|---|
| Petrol four-cylinder (316i, 318i, 320i, 330i) | 4 spark plugs — one per cylinder, as on any standard inline-four |
| Petrol six-cylinder (335i, 340i, M340i) | 6 spark plugs — genuinely a different engine family (BMW's inline-six), not a bigger version of the four-cylinder unit; confirm your exact engine code before ordering, since plug specification differs between the two families |
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Confirmed: A Genuine Technical Bulletin Worth Knowing About — BMW 3 Series Spark Plugs
If the engine has turned over but failed to actually start on a repeated cold-start attempt, this is genuinely worth knowing on models fitted with certain petrol engines: a confirmed technical bulletin identifies exactly this fault, where the car may start normally on the first attempt, but then fail to start if switched off immediately and tried again shortly after. The cause was identified as unfavourable engine management software combined with the original spark plug part fitted from the start of production, since superseded twice with revised versions.
It's also genuinely worth knowing a useful diagnostic technique: swapping a suspect coil to a different cylinder is a direct way to confirm whether a misfire is genuinely coil-related — if the misfire follows the coil, this confirms it; if it stays on the original cylinder, the cause is more likely the plug itself. It's also worth knowing that even fitting both a new plug and a new coil specifically to test hasn't always resolved a persistent, cylinder-specific misfire in documented cases, worth being prepared for further investigation if the fault doesn't clear after this.
BMW 3 Series 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 BMW Spark Plugs
The same part, covered across other BMW models.