2025 Nissan Altima — Spark Plug Type, Gap & Torque Specs

Quick reference

Note: 2025 Altima is coil-on-plug (no distributor). If your vehicle differs (fleet/export), always confirm by VIN.

Why the right plug matters

Choosing the correct spark plug for your Altima isn’t just about thread size. Heat range, tip design, and electrode material all affect drivability and longevity.

• Heat range: Nissan calibrates plug heat range to keep the insulator hot enough to self-clean but cool enough to prevent pre-ignition. Too hot a plug can cause knock and potential engine damage; too cold can foul and misfire. Always match the OE heat range.
• Electrode metal:
  • Iridium: Factory choice for the PR25DD. Ultra-fine center electrode with a hard, erosion-resistant tip for consistent spark at low voltage demand. Best longevity (often 100k+ mi) and stable idle on direct-injection engines.
  • Platinum: Acceptable in some applications but generally shorter life than iridium. If used, expect shorter intervals (60k mi typical) and ensure exact heat range and projection match OE.
  • Copper/nickel: Great conductivity but shortest life (20–30k mi). Not recommended for the PR25DD’s service interval or emissions requirements.

How to gap a spark plug

Most OE iridium plugs for the Altima come pre-gapped and should not be re-gapped aggressively. Still, always verify:

1. Use a wire-style gap gauge, not a coin wedge that can damage fine-wire tips.
2. Spec is 0.043–0.044 in (1.1 mm). A light touch is key—if adjustment is needed, bend the ground strap only. Do not pry against the iridium center electrode.
3. If a plug is outside spec or the fine-wire tip is damaged, replace it rather than attempting large corrections.

Replacement procedure tips (2.5L PR25DD)

The Altima’s 2.5L uses coil-on-plug (one coil per cylinder) and a gasketed, 12 mm thread plug in an aluminum head.

• Work cold. Aluminum heads are soft; remove and install plugs only on a cold engine to protect threads.
• Access: Remove the engine cover. Unplug each ignition coil connector carefully—Nissan connectors can turn brittle with age. Remove the 10 mm coil hold-down bolt and pull the coil straight up, twisting gently.
• Blow out the wells: Before loosening plugs, use compressed air to clear debris from plug tubes. This prevents dirt from falling into the cylinder.
• Removal: Use a 5/8 in (16 mm) spark plug socket with extension. Break loose smoothly. If a plug feels tight, add a small back-and-forth motion rather than forcing it.
• No anti-seize: Nissan and plug makers (NGK/Denso) advise against anti-seize on modern, nickel-plated shells. It alters torque and can lead to over-tightening. Install dry on clean threads.
• Torque: Hand-thread each plug 6–8 turns to avoid cross-threading, then torque to 13 lb-ft (18 Nm). If using a torque-angle method with a new crush washer and no torque wrench, seat lightly and turn an additional ~1/16–1/8 turn to crush—but a torque wrench is strongly preferred.
• Boots and grease: Inspect coil boots for carbon tracking or tears. A thin film of dielectric grease inside the boot can help future removal and seal out moisture; keep grease off the electrode end.
• Relearns: No special relearn is required after plug replacement. Clear any misfire codes and verify smooth idle.

Known issues

• Coil connectors and boots: With age/heat, coil connectors can crack and boots can carbon-track, causing intermittent misfires. Replace damaged boots or coils during plug service.
• Oil in plug tubes: Valve cover tube seals can seep, filling plug wells with oil and causing misfires. If present, replace the valve cover or tube seals before installing new plugs.
• GDI sensitivity: The PR25DD is direct-injected and can be sensitive to worn gaps. Small misfires at cold start often improve with fresh OE-spec iridium plugs.

(Notes on Ford two-piece plug breakage or GM ion-sensing coils do not apply to the Altima.)

Need plugs replaced? Find a shop on Repairius.