Top Signs Your Car’s Spark Plugs Need Replacement

Author: Yatharth Singh Chauhan•Published on: 1/8/2026•5 Minutes
Overview:You start your car one fine morning, twist the key (or press that start-stop button), and instead of that smooth sound of the engine, your vehicle starts jerking, and acting lazy. Frustrating, right? Many people start blaming the battery or even fuel quality, but the real culprit is often a tiny part inside your engine – the spark plug. Now, you might ask, what are spark plugs? And more importantly, when to change spark plugs? Don’t worry, we’ll break it down in the simplest way possible.
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Key Highlights:


  • Spark plugs may look tiny and inexpensive, but they play a crucial role in determining how well your car starts, runs, and uses fuel.
  • If your car's mileage suddenly drops, the plugs might be the hidden villain.
  • Jerks, misfires, and rough sounds are clear signs your spark plugs might be past their expiry date.
  • Changing spark plugs helps keep your engine healthy and prevents costly repairs later.



What are Spark Plugs?


Imagine you’re trying to light a gas stove at home. Without a spark, the gas won’t burn. Similarly, in a car, fuel needs a spark to burn inside the engine. That’s precisely what spark plugs do. They provide that tiny yet powerful spark that ignites the fuel-air mixture, allowing your engine to run.


Why Spark Plugs are So Important


People often overlook spark plugs because they are small and inexpensive. But don’t make that mistake. Bad spark plugs can:

  • Kill your mileage (and petrol prices are already killing us enough).
  • Make your car lazy like a Sunday afternoon.
  • Increase emissions.
  • Damage your engine in the long run.

Signs that Your Spark Plugs Need Replacement


Now comes the main point. How do you know that your spark plugs are crying for help? Here are the top signs:


1. Trouble Starting the Car

If your car struggles every morning, it could be because the spark plugs are worn out.


2. Poor Mileage

Earlier, you used to get 15 km/l; now it’s down to 11 or 12. A bad spark means incomplete fuel burn, which means wasted petrol.


3. Weird Engine Noises

If your car starts sounding rough, like phut-phut or tak-tak, chances are high the plugs are worn. A healthy engine purrs smoothly, but old plugs make it stumble.


4. Loss of Power While Driving

Pressing the accelerator, but the car still feels lazy? That’s again spark plugs not firing properly. Nothing feels worse than an overtaking gone wrong on the highway.


5. Warning Lights

Some modern cars even show a “check engine” light if plugs are misfiring. However, in desi cars like the Alto or WagonR, you’ll know just by how poorly the engine feels.


When to Change Spark Plugs?


This is the million-rupee question. There’s no fixed rule because it depends on your car and driving style. But generally:

  • Normal spark plugs: every 20,000 to 30,000 km.
  • Long-life iridium/platinum plugs: 80,000 to 1,00,000 km.

But don’t just wait for kilometres. If you notice the signs above, change them early. Prevention is always better than cure.


Link Between Spark Plugs & Oil and Filter Change


You must be wondering, “Why are we suddenly talking about oil and filter change?” Well, because the health of the spark plugs and engine oil is connected. Here’s how:

  • Old oil becomes dirty and can foul spark plugs.
  • If your air filter is clogged, the fuel-air mixture is incorrect, again affecting the spark plugs.

While you focus on car oil change frequency, remember that spark plugs also play a significant role in engine smoothness. If you skip the oil and filter change, spark plugs will also suffer.


Benefits of Timely Spark Plug Replacement


  1. Better Mileage – You’ll thank us when your petrol lasts longer.
  2. Smooth Driving – No more jerks or coughing engines.
  3. Faster Starts – No drama in the morning, just start and go.
  4. Longer Engine Life – Healthy plugs mean less strain on the engine.

Who Should Be Extra Careful?


  • City drivers are stuck in traffic daily. Stop-and-go driving wears plugs faster.
  • Highway runners who push their cars at high RPMs.
  • Old car owners, because chances are your car doesn’t even warn you.

Basically, everyone. Spark plugs don’t discriminate.


The Hidden Hero Under Your Hood


Spark plugs are like that superhero in regular clothes. Nobody pays attention until they’re gone, and suddenly everyone realises their importance. If you love your car (or even if you want to save fuel money), keep an eye on it.


So the next time your car feels lazy, don’t just blame the petrol price or traffic. Ask yourself: When should you change spark plugs? Maybe it’s time. And while you’re at it, don’t forget your regular oil and filter change. Because in the end, your car is like your body.


FAQs


1. What do spark plugs actually do in a car?
Spark plugs create a small spark that ignites the fuel-air mixture in the engine. This is what powers your car. Basically, they’re the “starter” of every engine party.


2. How do I know if my spark plugs need to be changed?
If your car starts having trouble starting, makes unusual noises, gives poor mileage, or displays a check engine light, the spark plugs may need replacement.


3. How often should spark plugs be replaced?
Depends on the type:

  • Normal plugs: Every 20,000-30,000 km
  • Iridium/Platinum plugs: 80,000-1,00,000 km

4. Can spark plugs affect my fuel mileage?
Yes, totally. Bad spark plugs can cause incomplete fuel burn, which means more petrol gets wasted.


5. What’s the link between spark plugs and the oil or air filter?
Dirty oil or a clogged air filter can mess with the engine, which then affects spark plugs, too.