Spark Plugs
easy DIY~1h jobWritten in plain English and reviewed by the eli5cars editorial team · Last reviewed June 2026
What it does
Spark plugs are like tiny lightning bolt makers at the top of each cylinder. Your engine mixes air and fuel, then a spark plug fires an electrical spark — exactly like a tiny lightning bolt — to ignite the mixture and push the piston down. Each plug fires thousands of times per minute. Over time, the metal tip that creates the spark erodes, the gap widens, and the spark becomes weak or inconsistent. When a plug misfires (fails to ignite the mixture), that cylinder produces no power and the engine runs rough.
Fix-vs-Skip Money Panel
DIY Cost
~$25
parts only
Shop Cost
~$150
parts + labor
Estimates only — real prices vary by region, vehicle, and shop. Updated 2026.
Buy the part
Heads up: some links below are affiliate links (including Amazon Associates) — if you buy through them we may earn a small commission at no extra cost to you. Details: /disclosure.
So what do I do now?
Three honest paths for fixing spark plugs — pick the one that fits your time, tools, and risk tolerance.
Door 1 — DIY it
Parts
Tools
- Spark plug socket + extension ($12–$25, one-time)
- Torque wrench ($35–$70, one-time)
- Spark plug gap gauge ($5–$10, one-time)
skip if your plugs come pre-gapped for your engine
Consumables
Anti-seize for plug threads (aluminum cylinder heads), Dielectric grease for the boot or coil connector
Watch out for
- Over-torquing a plug in an aluminum head can strip the threads — use a torque wrench, don't guess by feel
- On some V6/V8 engines the rear bank of plugs is buried under the intake manifold, turning an easy job into a 3-hour one
- Let the engine cool completely first — pulling plugs from a hot aluminum head risks stripping the threads
Skip DIY if: Skip DIY if your engine needs intake manifold removal to reach the rear plugs — check a forum thread for your exact engine before starting.
Heads up: some links below are affiliate links (including Amazon Associates) — if you buy through them we may earn a small commission at no extra cost to you. Details: /disclosure.
Door 2 — Buy the part
Already have someone lined up to install it (or handy friend), and just need the part?
Search Spark Plugs on AmazonHeads up: some links below are affiliate links (including Amazon Associates) — if you buy through them we may earn a small commission at no extra cost to you. Details: /disclosure.
Door 3 — Go to a shop
Fair price band
$113–$188
parts + labor, typical US pricing
Ask the shop
- Are the parts OEM or aftermarket?
- Is the diagnostic fee waived if I approve the repair?
- Can I get an itemized estimate before you start?
- What warranty do you offer on the labor?
DIY tutorial
Click to load video — helps keep this page fast
Frequently asked questions
How often should spark plugs be replaced?
Standard copper plugs: every 30,000 miles. Platinum plugs: every 60,000 miles. Iridium plugs: every 60,000–100,000 miles. Check your owner's manual for the specific interval for your car — many modern cars come with iridium plugs that don't need changing until 100k.
What does a misfiring spark plug feel like?
A rough idle (the engine vibrates or shakes at a stoplight), a stumble when you press the gas, reduced power on hills, and reduced fuel economy. A free OBD2 scan at AutoZone will show codes P0300–P0312 which identify the specific misfiring cylinder.
Can I damage my engine by driving with a bad spark plug?
Yes. An ongoing misfire sends raw, unburned fuel into the exhaust, which can destroy the catalytic converter ($1,500–$2,500 to replace). Fix misfires promptly — a set of plugs costs $20–$80.
Do I have to replace all spark plugs at once?
Yes. If one plug has reached the end of its service life, the others are at the same mileage and equally worn. Replacing all of them at once is the correct approach. Mixing old and new plugs leaves you with uneven combustion.