What Do Spark Plugs Actually Do, and When Should I Replace Them?
You’ve probably heard that spark plugs are an important part of your car, but what do they actually do? And how often should you replace them?
If your car struggles to start, uses more fuel than usual, or feels like it’s losing power, worn spark plugs could be the culprit. At Peers Auto Spares, we get these questions all the time — and in this blog post, we’ll break down what spark plugs do, how to know when they’re worn out, and how to choose the right replacements.
🔥 What Do Spark Plugs Do?
Spark plugs are small but essential components found in petrol engines. Their job is simple but critical:
They create a spark that ignites the air-fuel mixture in the engine’s combustion chamber.
This tiny explosion pushes the piston down, turning chemical energy (fuel) into mechanical energy (movement). Without a good spark, your engine won’t run properly — or at all.
💡 Diesel engines don’t use spark plugs — they rely on compression and glow plugs.
⚠️ Signs Your Spark Plugs Need Replacing
Spark plugs wear down over time. A bad spark plug may still spark, but not well enough to keep your engine running efficiently.
Here are common signs you might need new plugs:
1. Hard Starting
If your car struggles to start in the morning or turns over multiple times, it could be weak spark plugs.
2. Rough Idling or Misfiring
Does your engine feel shaky or inconsistent when idling? Misfires are often caused by worn spark plugs.
3. Poor Acceleration
A weak or delayed spark means the engine isn't firing properly, leading to sluggish response when you press the accelerator.
4. Increased Fuel Consumption
If your engine doesn’t burn fuel efficiently, you’ll use more fuel to travel the same distance.
5. Check Engine Light
Modern cars will trigger a fault code for misfires, often linked to old or faulty spark plugs.
📆 When Should You Replace Spark Plugs?
It depends on the type of spark plugs and your vehicle:
| Plug Type | Replacement Interval |
|---|---|
| Standard Copper | Every 30,000 – 40,000 km |
| Platinum/Iridium | Every 80,000 – 120,000 km |
Other factors that affect lifespan:
- Poor fuel quality
- Dirty air or fuel filters
- Driving mostly short distances
🔧 Not sure which type your car uses? Contact Peers Auto Spares and we’ll help you choose.
🔧 How to Replace Spark Plugs
If you’re comfortable with basic DIY tasks, you can replace spark plugs yourself. You’ll need:
- A ratchet with extension
- Spark plug socket
- Gapping tool (optional)
Steps:
- Disconnect the battery (for safety)
- Remove spark plug wires or ignition coils
- Unscrew the old plugs
- Check and adjust the gap on the new ones
- Install and torque to spec
If you're not sure or don’t have the tools, a mechanic can do it quickly and affordably — especially if you supply your own plugs.
🔍 How to Choose the Right Spark Plugs
Using the wrong spark plugs can lead to engine misfires, damage, or poor performance. Always make sure you buy plugs that match your car’s:
- Engine size
- Year and model
- Manufacturer specifications
✅ Want help picking the right plugs? Read our guide: How to Choose the Right Spark Plugs for Your Car
🛒 Where to Buy Spark Plugs in South Africa
At Peers Auto Spares, we stock spark plugs for:
- Toyota, VW, Ford, Nissan, Hyundai, BMW, and more
- Petrol and turbo petrol engines
- Trusted brands like NGK and Bosch
We offer:
- Great prices
- Fast delivery anywhere in SA
- Expert support to help you get the right plugs first time
🔧 Browse our spark plugs now or get a complete service kit with filters and plugs bundled together.
🧩 Related Parts for Smooth Engine Performance
When replacing spark plugs, it’s also a good time to check:
- Air filter – dirty air can affect combustion
- Fuel filter – protects injectors and flow
- Oil filter and oil – for full service performance
✅ Final Thoughts
Your car’s performance, fuel economy, and reliability all depend on something as small as a spark plug. Replace them on time and choose the correct ones to avoid misfires, starting problems, and fuel waste.
At Peers Auto Spares, we’re here to help you get the parts you need — with no guesswork.
🛍️ Order spark plugs online today or visit us in-store — we’ve got your car covered.
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