NGK 94201 Laser Iridium Spark Plug Set – BMW B58 Gen 1 / B46 / B48

OVERVIEW

The NGK 94201 (SILZKGR8B8S) is the OE-specification Laser Iridium spark plug for BMW's Gen 1 B46 / B48 four-cylinder and Gen 1 B58 six-cylinder turbo engines. Speed Logic stocks it for stock cars and for tuned applications on pump gas, E85 or water/methanol injection, including upgraded-turbo builds.

It pairs a fine-wire iridium center electrode with a projected square platinum pad on the ground electrode for even wear in coil-on-plug ignition systems. The laser-welded iridium tip is roughly six times harder than platinum, and the alumina ceramic insulator with a 98% pure copper core carries heat away from the firing end for reliable starts and long service life under boost.

Sold as a matched set — 4 plugs for the four-cylinder B46/B48 or 6 plugs for the six-cylinder B58 Gen 1. Speed Logic only sells genuine NGK spark plugs sourced through NGK's authorized distribution; counterfeits are common on eBay, Amazon and similar marketplaces.

SPECS

• Type: NGK Laser Iridium (High Ignitability)
• NGK stock number 94201 / plug number SILZKGR8B8S
• Heat range: 8 (OE heat range for B46 / B48 Gen 1 / B58 Gen 1)
• Thread size: M12 x 1.25
• Thread reach: 26.5 mm (1.043 in)
• Seat type: flat (gasket)
• Hex size: 14 mm 12-point (bi-hex)
• Center electrode: fine-wire iridium, copper core
• Ground electrode: projected square platinum electrode (PSPE), copper core
• Resistor: yes, 5 kΩ
• Gap: factory preset 0.030 in (0.75 mm); 0.022 in suggested for tuned / upgraded-turbo applications
• Direct OE-fit replacement — no tuning or ECU change required to install
• Sold as a matched set: 4 plugs (B46 / B48) or 6 plugs (B58 Gen 1)

PARTS INCLUDED

• Set of (4) genuine NGK 94201 Laser Iridium spark plugs — B46 / B48 Gen 1 four-cylinder engines, or
• Set of (6) genuine NGK 94201 Laser Iridium spark plugs — B58 Gen 1 six-cylinder engines (per variant selected)

TECH RESOURCES

• Additional parts required: None. NGK specifies no additional hardware for the NGK 94201 (SILZKGR8B8S); it is a direct drop-in replacement for the OE plug.
• Installer-supplied tools (not sold by Speed Logic): 14 mm 12-point (bi-hex) thin-wall spark plug socket — a standard 5/8" plug socket will not fit — plus a torque wrench and a wire/feeler gauge if you intend to adjust the gap.
• Installation: NGK does not publish a part-specific installation document for the NGK 94201. Follow NGK's official guidance: NGK Spark Plug Installation and NGK Electrode Gap Adjustment.
• Work on a cold engine. Blow debris out of the plug wells before removing the ignition coils, thread each plug in by hand until the gasket seats, then torque to the BMW factory specification for your engine (NGK's general figure for 12 mm gasket-seat plugs in aluminum heads is 15–20 Nm / 11–14.5 lb-ft). Do not apply anti-seize — NGK's trivalent-plated shell already prevents seizing and anti-seize leads to over-torquing.
• Gap: factory preset at 0.030 in (0.75 mm). Speed Logic suggests 0.022 in for tuned or upgraded-turbo cars; stock cars can run the factory gap. If you re-gap, adjust the ground electrode only with a proper gapping tool — never pry against the fine-wire iridium center electrode. Pre-gapped sets are available on request; contact Speed Logic with your setup.
• Clear any stored misfire codes after installation.
• Related NGK plugs: this part covers Gen 1 engines only — S58 and B58 / B48 Gen 2 (2019+ G-chassis) engines use the NGK 96206 Laser Iridium Spark Plugs; N20 / N26 / N54 / N55 / S55 engines use the NGK 97506 Laser Iridium Spark Plug Set.
• Install or gap questions? Contact Speed Logic — we also install in-house at our Westminster, CA shop.

PART NUMBER

• 94201 — NGK stock number
• SILZKGR8B8S — NGK plug number

VEHICLE APPLICATIONS