A tune, a bigger intercooler, a set of downpipes. Every one of them adds heat to the combustion chamber, and the factory spark plug was never picked with that in mind. When plugs run hot you get misfires and pre-ignition right when you are leaning on the car hardest.
The Dinan Iridium Spark Plug is built for the BMW B48, B58 and S58 engines, with a heat range 9 that runs one step colder than OEM. It pulls heat out of the chamber faster, resists pre-ignition, and needs less voltage to produce a strong spark. Dinan designed it for tuned cars, and it works on stock engines too.
Why a Colder Iridium Spark Plug Matters on a B58 or S58
The center electrode is tipped with iridium over a copper core. Iridium has a 152% higher melting point than silver, 125% higher than copper and 38% higher than platinum, so the tip keeps its shape under boost. The copper core moves heat away from the tip. Put the two together with a one-step-colder heat range and you get a plug that stays stable when a tuned B58 or S58 is making more cylinder pressure than stock.
Wondering if a colder plug will foul on a daily driver? Dinan states this plug is applicable to non-tuned, stock vehicles as well. It pairs directly with Dinan B Series Style ignition coils.
Iridium Spark Plug Specs and Legal Status
Each plug ships pre-gapped at 0.5mm with a flat seat and 14mm Bi-Hex, so it drops straight into the factory location. Made in the EU. Before you order, know this: it is not legal for sale or use in the State of California. Sold individually, so order one per cylinder. Dinan part number D640-0001. Sold by AutoTecknic, an authorized Dinan dealer.
What's Included
- One Dinan iridium spark plug, 12x26.5x14mm, flat seat, heat range 9
Key Features
- Heat range 9, one step colder than OEM on Gen 1 B48, Gen 1 and 2 B58, and S58
- Iridium center electrode tip with copper core
- Iridium: 152% higher melting point than silver, 125% higher than copper, 38% higher than platinum
- Resists pre-ignition and needs less voltage for a strong spark
- Suited to tuned and stock engines
- 12mm thread, 26.5mm reach, 14mm Bi-Hex, flat seat
- Supplied gap 0.5mm, install torque 17 Nm
- Replaces OEM 12120040551, 12122455258, 12120046646 and 12125A4EF60
- Made in the EU
Vehicle Fitment
Dinan lists this spark plug by engine family:
- BMW B48 (Gen 1)
- BMW B58 (Gen 1 and Gen 2)
- BMW S58
Not listed for later B48 or B58 generations. Check your engine generation, or match your current plug to the OEM numbers above, before ordering.
Installation Notes
Plug swaps are a basic DIY job with a spark plug socket, extension and torque wrench. The plugs come pre-gapped at 0.5mm, so check the gap but do not open it up. Work on a cold engine.
- Let the engine cool completely and remove the engine cover.
- Unplug and pull each ignition coil.
- Blow debris out of each plug well, then remove the old plugs.
- Thread each Dinan plug in by hand to avoid cross-threading.
- Torque to 17 Nm, then reinstall the coils and engine cover.
