NGK Iridium M117 and M116 spark plug as an alternative to the Bosch W9DC0 – Mercedes R107 W126 380SL 560SL USA

Description

NGK Iridium spark plug – high-quality upgrade for Bosch WR9DC / WR9DC0 – Mercedes M116 and M117 V8 engines

The NGK Iridium The spark plug is a high-quality upgrade for the Bosch WR9DC and WR9DC0 Spark plugs originally used in various Mercedes M116 and M117 engines. Thanks to the fine iridium center electrode, a more powerful and stable spark is generated, resulting in better combustion, smoother engine operation, a more reliable cold start, and a longer service life.

The original Bosch WR9DC spark plugs from the former German production are now hardly available anymore. Good Bosch NOS spark plugs are becoming increasingly scarce, causing prices to rise sharply. The NGK Iridium spark plug therefore represents an excellent alternative for those seeking maximum reliability and performance.

We regularly use these spark plugs in various Mercedes V8 engines, and the experiences are excellent. Especially in classics with low mileage, the powerful and stable ignition ensures noticeably smoother engine operation.

Suitable for, among others

• Mercedes R107 380 SL
• Mercedes R107 560 SL (USA version)

• Mercedes W126 380 SE / SEL
• Mercedes W126 560 SEL (USA version)

• Various Mercedes models with M116 and M117 engines with a lower compression ratio.

• Various export versions outside Europe.

Specifications

1. Brand: NGK.
2. Type: Iridium.
3. Thread size: M14 × 1.25.
4. Thread length: 19.0 mm.
5. Wrench size: 20.8 mm.
6. Seal: flat sealing ring.
7. Iridium center electrode.
8. Number of ground electrodes: 1.
9. SAE connection: screw-off.
10. Electrodeposition: 3.0 mm.
11. Alternative to Mercedes A0031591003 / 003159100326 / 0031591003 
12. Price is per piece.

Advantages

1. High-quality upgrade compared to conventional nickel spark plugs.
2. More powerful and stable ignition thanks to the iridium center electrode.
3. Better combustion and more efficient utilization of the air-fuel mixture.
4. Smoother engine operation and more reliable cold start.
5. Longer lifespan than conventional spark plugs.
6. Suitable for classic Mercedes M116 and M117 engines with a lower compression ratio.

Important

Before installation, always check that the prescribed heat number matches your engine specifications. In particular, different spark plug types may be prescribed for European and American versions of the M116 and M117 engines.

In case of doubt, we recommend checking the original Mercedes part number, engine number, or the engine compression ratio.

Always carefully inspect new spark plugs for transport or fall damage before installation. A dent or damage to the packaging may indicate that the spark plug has been hit hard. As a result, the ceramic insulation part may contain invisible hairline cracks.

Damaged ceramic can come loose during use and enter the combustion chamber, potentially resulting in serious engine damage. Therefore, install only spark plugs with completely undamaged ceramic.

Always check the spark plug electrode gap before installation. For most Mercedes M116 and M117 engines, an electrode gap of 0.8 mm recommended. Check each spark plug with a feeler gauge and correct the gap if necessary according to Mercedes factory specifications.

Although an iridium spark plug generally lasts considerably longer than a conventional spark plug, we recommend checking the spark plugs periodically and at the latest every 8 years or 30,000 kilometers to replace, depending on which is reached first or when Mercedes prescribes a shorter replacement interval.

Always check before purchase and installation whether the part is suitable and equivalent based on photos, description, and specifications; installed or used parts cannot be returned.