The vast majority of Nissan spark plugs use a 5/8 inch (16mm) hex, so a 5/8" spark plug socket is the standard choice for most Nissan engines.
However, there are exceptions depending on the model and engine family. Some older or regional variants may use a different hex size, such as 14mm or 13/16 inch (21mm). Always verify the exact plug hex size for your specific Nissan engine by checking the service manual or inspecting the spark plug head itself.
Common Nissan spark plug hex sizes by engine family
The following list highlights the sizes you’re most likely to encounter on popular Nissan engines. Use this as a guide, but confirm with your vehicle’s official specifications if in doubt.
- 5/8 inch (16mm) hex: This is the standard size for many modern Nissan engines (for example QR-series, MR-series, VQ-series in models like Altima, Maxima, Sentra, 370Z, and more). A typical spark plug socket in 5/8" with a 3/8" or 1/2" drive is usually used.
- 13/16 inch (21mm) hex: Some older or less common Nissan engines may employ a larger hex on the spark plug head.
- 14mm hex: A smaller hex size found on a subset of rare or overseas variants; if your engine uses 14mm plugs, you’ll need a 14mm spark plug socket.
Because hex sizes vary by model year and market, always double-check the plug hex size before purchasing tools. If you’re unsure, inspect the plug head or consult your engine’s official service information for your specific vehicle.
How to verify the correct socket size
Measure the plug head across the flats with calipers or a precise ruler, or compare the plug head to sockets in your toolkit to see which size fits snugly without forcing. If the plug is difficult to turn or you notice rounding on the plug head, stop and confirm the exact size to avoid damage.
Summary
For most Nissan vehicles, a 5/8 inch (16mm) spark plug socket will be the correct choice. Always verify the exact hex size for your engine model and year, especially for older or regional variants that may use 14mm or 13/16 inch (21mm) plugs. When in doubt, consult the service manual or parts diagram for your specific engine code.