Bosch 9779 Spark Plug

Bosch OE Fine Wire Iridium Spark Plug 9779

Bosch 9779 is an OE Fine Wire Iridium spark plug built for precise ignition performance and extended service life. It uses an ultra-fine iridium center electrode, a platinum ground electrode tip, and a resistor design to support stable spark delivery in modern 4-cycle engines.

Compatible With Subaru Crosstrek, Forester, Impreza, Outback, and Legacy applications listed below, this Bosch spark plug is a direct secondary ignition service part for select Subaru models. The OE Fine Wire Iridium line focuses on OE-style fit and ignition consistency for everyday driving and long-term maintenance intervals.

Key Features

• Part number 9779 Bosch spark plug for secondary ignition service
• Iridium fine-wire center electrode for focused spark delivery
• Platinum ground electrode tip with standard J-gap configuration
• Resistor type plug with 6000 resistance specification
• Projected ceramic insulator for modern engine applications
• 12 mm thread diameter, 14 mm hex, flat seat design
• Pre-gapped to .7 for the listed application
• 4-cycle spark plug construction for gasoline engine use

OE Fine Wire Iridium Line

Bosch OE Fine Wire Iridium spark plugs are part of Bosch’s OE-focused ignition lineup. The fine-wire iridium firing pin is used to promote consistent ignition performance, while the platinum-tipped ground electrode supports durability in demanding daily-use engines. Bosch 9779 follows the OE-style dimensions and heat range needed for select Subaru engines.

Vehicle Fitment

• Fits 2025-2026 Subaru Crosstrek, N/A, OE Fine Wire Iridium
• Fits 2018-2023 Subaru Crosstrek, N/A, OE Fine Wire Iridium
• Fits 2025-2026 Subaru Forester, N/A, OE Fine Wire Iridium
• Fits 2019-2023 Subaru Forester, N/A, OE Fine Wire Iridium
• Fits 2025-2026 Subaru Impreza, N/A, OE Fine Wire Iridium
• Fits 2022-2023 Subaru Impreza, N/A, OE Fine Wire Iridium
• Fits 2017-2020 Subaru Impreza, N/A, OE Fine Wire Iridium
• Fits 2025-2026 Subaru Outback, N/A, OE Fine Wire Iridium
• Fits 2022-2023 Subaru Outback, N/A, OE Fine Wire Iridium
• Fits 2020 Subaru Outback, N/A, OE Fine Wire Iridium
• Fits 2025 Subaru Legacy, N/A, OE Fine Wire Iridium
• Fits 2022-2023 Subaru Legacy, N/A, OE Fine Wire Iridium
• Fits 2020 Subaru Legacy, N/A, OE Fine Wire Iridium

What It Helps Address

• Misfire concerns related to worn spark plug electrodes
• Hard starting caused by degraded ignition performance
• Rough idle from inconsistent spark delivery
• Reduced throttle response from aged secondary ignition components
• Maintenance replacement for Subaru Crosstrek, Forester, Impreza, Outback, and Legacy tune-ups

Installation Notes

Verify engine application by year, make, and model before installation. Confirm the 12 mm thread diameter, 14 mm hex, flat seat, and .7 pre-gap match the engine specification. Use proper spark plug service procedures and torque to the vehicle manufacturer’s specification. Bosch 9779 is listed for select Subaru Crosstrek, Forester, Impreza, Outback, and Legacy applications.

Quality Assurance

Bosch manufactures this spark plug to OE-style specifications for fit, heat range, and ignition performance in the listed Subaru applications. Part number 9779 is built with iridium and platinum electrode materials to support long service life in secondary ignition service.