Spark plugs are often overlooked in routine maintenance — they're small, hidden under covers, and tend to fail gradually rather than suddenly. But worn spark plugs can cause rough running, misfires, poor fuel economy, and hard starting. Replacing them at the right interval keeps your engine running cleanly.
What Do Spark Plugs Do?
Spark plugs ignite the air-fuel mixture in your engine's combustion chambers. Each plug fires thousands of times per minute. Over time, the electrode erodes, the gap widens, and the plug requires more voltage to fire — eventually causing misfires.
How Long Do Spark Plugs Last?
Service life depends heavily on the plug type:
- Copper spark plugs — 30,000–40,000 km (less common in modern vehicles)
- Platinum spark plugs — 60,000–80,000 km
- Iridium spark plugs — 100,000–120,000 km (most modern vehicles)
Check your owner's manual for the specified interval and plug type. Using the wrong plug type can cause performance issues.
Signs Your Spark Plugs Need Replacing
- Rough idling or engine vibration
- Hesitation or stumbling during acceleration
- Poor fuel economy
- Hard starting — especially on cold Perth winter mornings
- Engine warning light (misfires trigger fault codes)
- Engine misfires under load
What's Involved in Spark Plug Replacement?
On straightforward engines (inline 4-cylinders with easy access), spark plug replacement takes 30–60 minutes. On V6 and V8 engines, or those with tight engine bays, it can take 2–4 hours due to access difficulty. European vehicles with coil packs integrated into the plug wells add complexity.
Spark Plug Replacement Cost in Perth
- 4-cylinder engine — $80–$200 parts and labour
- 6-cylinder engine — $150–$350
- V8 engine — $200–$450
Iridium plugs cost more than copper or platinum in parts, but their longer lifespan typically makes them better value. Labour rates in Perth range from $100–$180 per hour depending on the workshop.
Ignition Coils
Spark plugs work with ignition coils. If a coil fails, the plug it serves won't fire — causing a cylinder misfire. Coil failure is common in older vehicles and often triggers a specific fault code. When replacing plugs on a high-mileage vehicle, it's worth having coils tested at the same time.
Book Your Spark Plug Service in Perth
If your car is overdue for a spark plug change or you're experiencing any of the symptoms above, a Perth mechanic can inspect and replace plugs quickly. It's one of the best value maintenance items you can do for engine performance and fuel economy.