Dinan Iridium Spark Plug – Heat Range 9 | 2025+ BMW Gen2 B48 / Gen3 B58 | D640-0003

Sold as a single plug. Order 4 for a complete B48 (4-cylinder) set. Order 6 for a complete B58 (6-cylinder) set.

2025+ Gen2 B48 and Gen3 B58 only. Verify your exact engine generation before ordering — earlier B48 and B58 variants require a different plug specification.

Dinan D640-0003 iridium spark plug for 2025+ BMW Gen2 B48 and Gen3 B58 engines. Heat range 9 (cooler spec) for tuned and modified applications. 12mm thread × 26.5mm reach × 14mm hex. 0.1 lbs per plug. Ships fast across Canada and the US.

Dinan Iridium — Heat Range 9

Dinan’s iridium spark plugs use an iridium-tipped centre electrode with a copper core — iridium’s higher melting point and hardness compared to platinum or nickel alloy electrodes allows a finer tip diameter for more consistent spark formation, lower required ignition voltage, and extended service life. The copper core improves heat transfer away from the electrode tip, keeping operating temperature within the correct range across the power band.

Heat range 9 is a cooler specification than the OEM plug heat range for the B48 and B58. A cooler plug transfers heat away from the electrode tip more rapidly — appropriate for tuned engines running elevated boost pressure, modified fuel maps, or increased cylinder temperatures where a standard heat range plug may run too hot and risk pre-ignition from a glowing electrode tip. Confirm the correct heat range for your specific tune and boost level with your tuner before selecting plugs — running a plug that is too cold on a lightly modified or stock engine can cause fouling.

Physical Specifications

• Thread diameter: 12mm
• Thread reach: 26.5mm
• Hex size: 14mm

Confirm these dimensions match your engine’s plug bore specification before ordering. The thread reach (26.5mm) must match the head’s plug bore depth — an incorrect reach causes the plug to seat incorrectly and can damage the thread or combustion chamber.

2025+ Gen2 B48 / Gen3 B58 Applications

This plug is spec’d for the 2025+ generation of BMW’s B48 (4-cylinder) and B58 (6-cylinder) turbocharged engines — the Gen2 B48B20 and Gen3 B58B30 variants used in the current G-series 3 Series, 4 Series, M240i, M340i, M440i, X3, X5, and related platforms. Owners of earlier B48 or B58 vehicles (pre-2025 applications) should confirm their engine generation and verify plug fitment against Dinan’s current application guide before ordering.

Single plug — order 4 for B48 full set, order 6 for B58 full set. Verify engine generation (Gen2 B48 / Gen3 B58) before ordering. Gap to your ignition system’s specification — do not assume factory gap is correct for a tuned application. Torque to BMW specification — do not overtorque iridium plugs. Confirm heat range with your tuner for modified applications.

Specifications

• Brand: Dinan
• Part Number: D640-0003
• Type: Iridium spark plug
• Heat Range: 9 (cooler — tuned applications)
• Thread: 12mm
• Reach: 26.5mm
• Hex: 14mm
• Quantity: Single
• Weight: 0.1 lbs
• Application: 2025+ BMW Gen2 B48 / Gen3 B58