Spark Plug Replacement Guide: Tools, Gap, and Torque
Follow the spark plug replacement interval in your owner's manual. Worn plugs can cause misfires (P030x codes, see reading codes), rough idle, and lower fuel economy.
Tools
- A spark plug socket (it has a rubber insert or magnet to hold the plug) in the right size for your plugs, plus extensions
- A torque wrench in the right range. See the torque wrench guide.
- A gap gauge, if your plugs need gapping. Many come pre-gapped, so verify against your vehicle's spec.
- Dielectric grease for the coil boots, and compressed air
Procedure
- Work on a cold engine. Aluminum heads are easily damaged when hot.
- Remove one coil and plug at a time to avoid mixing up cylinders.
- Blow debris out of the plug well before removing the plug.
- Start threading the new plug by hand to avoid cross-threading.
- Torque to spec. Don't use anti-seize unless the plug or vehicle maker recommends it, because it changes the effective torque.
Read the old plugs
Oil fouling, heavy carbon, or a damaged electrode can point to a separate problem worth diagnosing.
| Product | Best for | What to look for | Price |
|---|---|---|---|
| Spark plug socket set | Removing and installing plugs | Correct sizes, retaining insert | Check current price at your retailer |
| 3/8" torque wrench | Correct plug torque | Range that covers plug specs | Check current price at your retailer |
| Spark plug gap tool | Checking the gap | Wire or feeler style; avoid tapered coin gauges on fine-wire plugs | Check current price at your retailer |
| Dielectric grease | Coil boots | Small tube | Check current price at your retailer |
Research-based roundup of product categories. We have not lab-tested these products. Confirm specs and fitment on the retailer's listing.