In most Infiniti G35 models powered by the VQ35DE engine, you should plan to replace spark plugs roughly every 105,000 miles (about 169,000 kilometers) when using iridium or platinum plugs. If you opt for copper plugs, expect a much shorter interval and more frequent maintenance. Driving conditions, climate, and maintenance history can influence this timing, so use it as a baseline and adjust based on performance symptoms and your manual.
What the manufacturer recommends for the G35
The G35’s VQ35DE engine has historically used long-life, center-electrode spark plugs (typically iridium or platinum) rated for extended intervals. Infiniti/Nissan manuals and dealership service bulletins commonly cite a replacement interval around 105,000 miles for these plug types. If your car originally came with copper plugs—or you install copper replacements—the life expectancy is shorter and you should inspect or replace more frequently. Always check your owner’s manual and the specific plug packaging for the exact gap and torque specifications, and follow the official guidance for the exact model year and transmission/engine variant.
Typical intervals by plug type
Below is a practical guide to the common plug types found in G35s and the expected replacement timing. Note that actual intervals can vary based on driving habits and service history.
- Iridium or platinum spark plugs: about 105,000 miles (169,000 km).
- Copper spark plugs (if installed): significantly shorter life; not generally recommended for the G35’s VQ35DE unless you are balancing cost against longer service intervals.
These intervals reflect common industry practice and manufacturer guidance for long-life plugs. When in doubt, defer to the plug manufacturer’s recommended gap and the vehicle’s service manual, and consider a dealer or qualified technician’s recommendation based on your specific year and engine variant.
Driving conditions and signs you may need replacement
Even if you’re within the nominal interval, certain driving conditions and symptoms can shorten spark plug life or indicate that a replacement is due sooner. High-load driving, frequent short trips, extreme heat, towing, or frequent idling can all impact plug longevity. Watch for the following indicators that suggest it’s time for a plug change.
- Rough idle or hesitation during acceleration
- Engine misfires or a noticeable drop in smoothness
- Deteriorated fuel economy or reduced engine performance
- Difficulty starting or persistent crank/no-start conditions
- Illuminated check engine light with misfire-related codes (e.g., P030x series)
If you notice any of these symptoms, have the plugs inspected promptly. Early replacement can prevent further engine wear and maintain performance.
How to replace spark plugs on the G35
Replacing spark plugs on the G35 is a manageable job for a competent DIYer, but the VQ35DE uses coil-on-plug ignition and tight clearances in the cylinder head. If you’re not comfortable with basic hand tools, torque specs, and gasket safety, consider having a professional perform the service.
- Disconnect the negative battery terminal to prevent any electrical shorts while you work.
- Identify the ignition coils for each cylinder and label or photograph their orientation to ensure proper reinstallation.
- Carefully detach each coil-on-plug assembly, one cylinder at a time, to access the spark plugs. Avoid forcing wires or damaging the coil boots.
- Clean the spark plug wells around each opening to prevent debris from falling into the combustion chamber.
- Install a spark plug socket with a deep-well extension and a ratchet. Gently loosen and remove the old plug, keeping the surrounding area clean.
- Compare the old plug with the new one to verify thread length and reach. Use OEM or OEM-recommended iridium/platinum plugs and check the gap if they are not pre-gapped by the manufacturer.
- Install the new plug and tighten to the manufacturer’s specified torque. Do not overtighten, as overtightening can damage the cylinder head threads.
- Reinstall the ignition coil/boot and reconnect any electrical connectors. Repeat for each cylinder, ensuring all coils are properly seated.
- Reconnect the battery, start the engine, and listen for misfires. If the check engine light returns or a rough idle persists, recheck coil connections and plug seating.
Because torque specs and gap settings matter for proper sealing and performance, consult your service manual or OEM plug packaging for the exact figures. If you’re unsure, have a professional technician perform the replacement to avoid cross-threading or misfires.
Choosing the right plugs for your G35
Most G35 owners opt for OEM-equivalent iridium or platinum plugs designed for long life and reliable performance. Using the correct heat range and connector type is crucial for smooth operation of the VQ35DE’s coil-on-plug system. If you’re restoring an older example or have modified the engine, verify compatibility with your specific model year and any aftermarket improvements. Always use high-quality plugs from reputable brands and replace with deposits-free hardware to maintain a clean ignition system.
- Stick with OEM- or manufacturer-approved iridium/platinum plugs for best longevity and reliability.
- Avoid copper plugs for the VQ35DE if possible, as life and performance typically lag behind long-life options.
- Check the recommended gap and installation torque in your owner’s manual or the plug packaging, and adjust only as specified.
Choosing the right plugs can help maximize performance, fuel efficiency, and engine longevity while minimizing the frequency of maintenance. If you drive aggressively or in extreme conditions, you may benefit from more frequent checks within the guideline interval.
Summary and takeaways
For the Infiniti G35 with the VQ35DE engine, plan spark plug replacement around every 105,000 miles when using iridium or platinum plugs. Copper plugs require much more frequent service and are not generally recommended for this engine. Monitor for symptoms such as rough idle, misfires, or fuel economy loss, which can signal a need for replacement sooner. When replacing, follow proper torque specifications and use OEM-compatible plugs, and consider professional service if you’re unsure about the coil-on-plug setup. Regular maintenance and sticking to recommended intervals help preserve performance, efficiency, and engine longevity.
Bottom line
In practice, use the 105,000-mile benchmark as your baseline for G35 spark plugs, but stay attentive to driving conditions and engine behavior. With proper care, you’ll keep the VQ35DE running smoothly for many miles to come.