Buy Hummer H2 Spark Plugs

Spark plugs create the tiny lightning bolt that fires the H2's big V‑8 every time the piston comes up to the top. When the gap is right and the plug is clean, combustion is strong, fuel burns completely, and the SUV keeps its power and fuel economy. A worn or fouled plug makes the truck stumble, waste gas, and even trigger the check‑engine light. The H2's plugs are easy to reach with common tools, making this a smart DIY maintenance job.

• Fits 2003‑2007 6.0 L LQ4 V‑8 and 2008‑2009 6.2 L L92 V‑8 H2s  (SixityAuto.com)
• Eight identical plugs per engine (one per cylinder)  (SixityAuto.com)

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Tip: Hand‑thread every ignition plug first; then use a torque wrench to finish snugly. Over‑tightening can crack the porcelain; under‑tightening can make the plug run hot. The Champion torque chart shows the same values for gasket‑type plugs. 

• GM's long‑life iridium plugs are rated for 97,500 miles in similar LS‑family engines  (Reddit)
• Real‑world owners often swap at 80‑100 k miles for best performance  (hummerforums.com)
• Replace sooner if you notice:
  • Rough idle, slow starts, or misfire  (YouTube)
  • Falling fuel economy or sluggish acceleration  (championautoparts.com)

Skipping service lets carbon build up and may trigger the check‑engine light; see the Car Care Council's advisory on common CEL repairs. 

• Copper‑core: lowest cost, best conductivity, lasts ~30 k miles.
• Platinum: fine‑wire tip doubles life vs. copper.
• Iridium: hardest electrode; up to 25 % longer life than platinum  (championautoparts.com)

A quick primer on heat range is on NGK's heat‑range guide . Cooler plugs pull heat away faster; hotter plugs keep more heat for cleaner firing.

1. Let the engine cool completely-aluminum heads warp when hot.
2. Remove the coil‑on‑plug boots and blow out dust.
3. Using a 5/8‑inch socket, loosen each old plug.
4. Check the new plug's gap-should already read 0.040 in  (downloads.innova.com).
5. Twist in by hand, then torque to 11 lb‑ft.
6. Reinstall coils, clear any stored codes, and test‑drive.

A full walk‑through video is here: "Easy H2 Spark Plug Replacement" .

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• Use a dab of dielectric grease inside each coil boot for easy removal next time.
• Keep fresh air and fuel filters; dirty filters accelerate plug fouling  (Be Car Care Aware).
• Avoid anti‑seize on the threads-modern plugs already have a special coating  (Silverado Sierra).

Healthy plugs cut unburned fuel, lowering exhaust hydrocarbons. Worn plugs can waste up to 30 % more fuel  (MediaRoom), so timely maintenance helps both your wallet and the planet.

Q: What size wrench do I need?
A: A standard 5/8‑inch (16 mm) spark‑plug socket fits H2 plugs and most GM LS engines  (CarParts).

Q: Can I close or open the gap on iridium plugs?
A: GM says no-iridium fine wires can crack. Buy plugs pre‑gapped to 0.040 in  (downloads.innova.com).

Q: My older manual says 0.060 in gap. Which do I trust?
A: Trust the revised GM service bulletin that supersedes that spec to 0.040 in .

Q: How tight is "tight enough"?
A: Use a torque wrench set to 11 lb‑ft; too much force can strip aluminum threads  (JustAnswer).

Q: What plug brand is best?
A: Any high‑quality iridium plug that meets GM spec works. The key is correct heat range and gap  (championautoparts.com).

Q: Do I need new wires?
A: The H2 uses coil‑on‑plug boots instead of long wires; inspect boots for cracks during plug service  (YouTube).

Q: Will better plugs add horsepower?
A: Fresh plugs can restore lost power, but won't exceed factory output unless your old ones were failing  (YouTube).

Q: How can I tell if a plug is fouled?
A: Look for black carbon, oily residue, or a burnt electrode. Compare to photos in Champion's troubleshooting guide .

Q: Are iridium plugs worth the cost?
A: Yes-iridium lasts about 25 % longer than platinum and keeps its gap better, saving labor down the road  (championautoparts.com).

Q: What happens if I ignore misfires?
A: Persistent misfire can overheat the catalytic converter and ruin it-an expensive fix  (MediaRoom).

Want more basics on vehicle upkeep? Check the Car Care Council's plain‑language Vehicle Systems Overview for handy maintenance charts .