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NGK 5666 Spark Plug
| Brand | NGK 5666 |
|---|---|
| Resistance | 5000 |
| Ground Electrode Tip Design | Standard |
| Ground Configuration | Standard |
| Ground Electrode Core Material | Nickel |
| Electrical Terminal Type | Stud |
| Center Electrode Core Material | Copper |
| Center Electrode Tip Material | Nickel |
| Pre-Gap Size | .036 |
| Ground Electrode Quantity | 1 |
| Hex Size | 5/8 |
| Insulator Height | 50.00 |
| Manufacturer Heat Range | 8 |
| Seat Type | Flat |
| Reach | .75 |
| Thread Diameter | 10.00 |
| Part Number | Cr8eh-9 |
| Stock Number | 5666 |
| Fits | — |
OE-quality design. Built to original equipment standards for dependable performance.
Copper core. Helps promote consistent ignition and efficient spark delivery.
Standard spark plug. A direct-fit replacement for routine ignition service.
Cross-references DENSO Auto Parts 4127, Monroe Shocks & Struts 5666 and 98059-58916 for the same application. See all 6.
NGK CR8EH-9 Spark Plug for Reliable Ignition
The NGK Standard Spark Plug 5666 is built for consistent ignition performance in a wide range of automotive, motorcycle, marine, and small engine applications. As an NGK spark plug, part number CR8EH-9, it combines OE-focused construction with the materials and dimensions needed for stable combustion and dependable starts.
Key Features
- NGK Standard Spark Plug, part number 5666 / CR8EH-9
- Copper center electrode core with nickel center electrode tip
- Nickel ground electrode with standard tip and standard configuration
- 5,000 ohm resistance for ignition system noise control
- Pre-gapped to .036 inch
- 10.00 mm thread diameter, .75 inch reach, flat seat
- 5/8 hex size and stud terminal type
- Manufacturer heat range 8
Product Details
NGK builds this Standard Spark Plug line around OE-style durability and consistent operational performance. The CR8EH-9 uses a copper core for efficient heat transfer, nickel electrode materials for dependable service, and a standard ground electrode layout that supports stable spark delivery. For drivers searching for an NGK 5666 spark plug or CR8EH-9 replacement, this plug is a direct match to the listed specifications and is suited to applications that call for a 10 mm, flat-seat plug with a .036 inch gap.
This part cross-references DENSO Auto Parts 4127 for the same application. It is also associated with Monroe Shocks & Struts 5666 in interchange listings.
Common Issues This Spark Plug Can Address
- Hard starting caused by worn or fouled spark plugs
- Rough idle from weak or inconsistent spark output
- Misfire conditions related to electrode wear
- Reduced fuel efficiency from incomplete combustion
- Ignition noise concerns where resistor-style plugs are specified
Installation Notes and Tips
Verify the vehicle’s required thread diameter, reach, seat type, heat range, and terminal style before installation. Check the gap against the engine specification even though this plug is pre-gapped to .036 inch, and inspect the ignition coil, wires, or boots for wear that could affect performance. For fitment-based searches, this NGK spark plug is a common choice for drivers looking for a CR8EH-9 spark plug for Honda Civic, Honda Accord, or similar vehicle applications where the listed dimensions match the engine requirement.
Quality Assurance
NGK is a long-established OE supplier with North American manufacturing and distribution support, and its spark plugs are produced to original-equipment standards for durability and consistent operation. The Standard Spark Plug line reflects NGK’s focus on reliable ignition performance across automotive, motorcycle, marine, and small engine use cases.
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|---|---|---|---|---|
| No rows match your filter. | ||||