Quick answer: Replacing spark plugs typically costs $100–$300 on a 4-cylinder engine and $250–$600+ on a V6 or V8, especially when the rear plugs are under the intake manifold. Most modern iridium or platinum plugs last 60,000–120,000 miles.
Spark plug replacement cost by engine
Estimates updated October 2026, independent shop prices with labor at $100–$200 per hour.
| Engine | Plugs (set) | Labor hours | Typical total | Dealer |
|---|---|---|---|---|
| 4-cylinder, easy access | $40 – $120 | 0.5 – 1.5 | $100 – $300 | $200 – $400 |
| V6, transverse (rear plugs under intake) | $60 – $180 | 1.5 – 3.5 | $250 – $600 | $400 – $800 |
| V8 | $80 – $200 | 1.5 – 4 | $250 – $700 | $400 – $900 |
| Some trucks with known plug-removal issues | $80 – $200 | 2 – 6 | $400 – $1,000+ | — |
| DIY (4-cylinder) | $40 – $120 | — | $40 – $120 | — |
Shops often recommend replacing ignition coils or coil boots at the same time on high-mileage engines ($150–$500 extra), but it’s not always necessary.
When to replace spark plugs
Follow your owner’s manual. Typical intervals:
- Copper plugs: around 30,000 miles (mostly older cars).
- Platinum / iridium plugs: 60,000–120,000 miles in most modern engines.
- Turbocharged engines often need plugs sooner.
Signs of worn spark plugs
- Rough idle or shaking at a stop.
- Misfires and a check engine light, often codes P0300–P0308; see P0300 Code: Random Misfire.
- Hard starting, especially in cold weather.
- Poor acceleration and lower fuel economy.
Why plugs cost more on some engines
On many transverse V6 engines, the three rear plugs sit under the intake manifold, so the shop must remove the intake (and replace its gaskets) to reach them. Some engines are also known for plugs that seize or break during removal, which increases labor.
How to save money
- Use the plug type and brand specified by your manufacturer (often NGK or Denso).
- Do plugs at the same visit as other work that requires removing the intake.
- On easy 4-cylinder engines, plugs are a common DIY job; use a torque wrench and avoid cross-threading.