NGK 5686 Spark Plug

NGK Iridium IX Spark Plug for BMW Performance

The NGK Iridium IX Spark Plug, part number 5686, is built for precise ignition performance in select BMW applications. It combines an iridium center electrode with a nickel ground electrode and a 5,000-ohm resistor to support stable spark delivery and consistent combustion.

Compatible with 1987-1988 BMW M6, 1988 BMW M5, and 1988-1991 BMW M3 applications, this NGK spark plug is a direct-fit ignition service part for drivers maintaining factory-style operation. The DR7EIX part number is also referenced as 5686 in aftermarket catalogs.

Key Features

• Iridium center electrode tip material for durable spark performance
• Copper center electrode core for efficient conductivity
• Nickel ground electrode core with standard ground configuration
• Taper cut ground electrode tip design for focused spark exposure
• 5,000-ohm resistance for ignition system noise control
• Flat seat design, 12 mm thread diameter, and 0.75 in reach
• Pre-gapped to 0.032 in from the factory
• Heat range 7 for specified engine applications

Product Details

NGK’s Iridium IX line is engineered around a fine iridium firing tip and OE-focused construction for dependable ignition service. For BMW M3, BMW M5, and BMW M6 applications, the 5686 spark plug supports consistent starting, smooth idle quality, and reliable combustion under normal driving conditions. The stud terminal, 18 mm hex size, and flat seat configuration match the listed fitment requirements for these vehicles.

This part cross-references DENSO Auto Parts 5371 for the same application.

Common Issues This Part Can Help Address

• Hard starting caused by worn spark plugs
• Rough idle from inconsistent spark delivery
• Misfire symptoms related to degraded plug electrodes
• Reduced combustion efficiency from excessive plug wear
• Ignition noise concerns in resistor-equipped systems

Installation Notes and Tips

Verify the vehicle application before installation and confirm the specified gap for your engine. Listed fitment notes call for a 0.024 in gap on 1988 BMW M5 and 1987-1988 BMW M6 applications, and a 0.028 in gap on 1988-1991 BMW M3 applications. Use the correct torque procedure for the cylinder head material and inspect ignition components during service.

Quality Assurance

NGK is a long-established OE supplier and ignition specialist with broad coverage across automotive applications. The brand’s manufacturing and distribution network supports consistent product standards for replacement spark plugs such as the NGK 5686.