How Often Should You Change Spark Plugs?

If you’ve ever wondered when to swap out those tiny metal things in your engine, you’re not alone. Spark plugs are cheap, but ignoring them can cost you big in fuel and power. Let’s break down the basics so you can keep your car humming without guesswork.

Signs Your Spark Plugs Need Replacing

First off, your car will give you clues. A rough idle, misfires, or a noticeable drop in acceleration? Those are classic red flags. If the check‑engine light flashes with a code related to ignition, that’s another hint. You might also notice a higher fuel consumption – the engine is working harder because the spark isn’t strong enough.

Listen for a popping or ticking sound when you rev the engine; that often means the plug gaps are worn. Finally, if you’ve hit the mileage that the manufacturer recommends (usually every 30,000 – 100,000 miles), it’s a good idea to check them even if the car feels fine.

How Many Miles Between Replacements?

Most car makers suggest changing spark plugs every 30,000 to 60,000 miles for copper plugs, while iridium or platinum plugs can stretch to 100,000 miles. Your driving style matters – frequent short trips, stop‑and‑go traffic, or towing puts extra stress on the plugs.

Don’t rely solely on mileage, though. Age can be a factor too. A plug left in an engine for years can corrode, even if you haven’t hit the mileage target. Think of it like a battery – time and use both wear it out.

When in doubt, pull one plug and inspect it. A clean, light tan colour means it’s still healthy. Dark, carbon‑filled or oily deposits signal it’s time for a new one.

Changing spark plugs is a quick DIY job for most drivers. You’ll need a socket, a plug gap gauge, and maybe a dielectric grease. Remove the old plug, check the gap on the new one (usually listed in the manual), and hand‑tighten before giving it a final snug turn. Too tight can crack the cylinder head, too loose can cause misfires.

Why bother? Fresh plugs give a stronger, more consistent spark, which improves combustion. That translates to smoother acceleration, better fuel economy, and reduced emissions. In extreme cases, bad plugs can damage the catalytic converter – a costly repair you can avoid.

Cost‑wise, a set of copper plugs runs around £20‑£30, while iridium sets can be £70‑£100. Labor at a garage is typically £40‑£80, but many drivers save time and money by doing it themselves.

Remember, the type of plug matters for your engine. Modern cars often come with iridium or platinum plugs from the factory, designed for longer intervals. Swapping them for cheaper copper ones just to save a few pounds can backfire with more frequent changes.

Here’s a quick cheat‑sheet:

• Check the owner’s manual for the recommended interval.
• Inspect plugs every 20,000 miles if you drive a lot in city traffic.
• Replace if you see rough idle, misfire, or fuel‑economy drop.
• Use the correct gap – most new plugs are pre‑gapped, but double‑check.
• Apply a tiny dab of dielectric grease on the threads for easier removal later.

Bottom line: don’t wait for the engine to scream. Keep an eye on performance, note the mileage, and change spark plugs on schedule. Your car will thank you with smoother rides, better mileage, and fewer surprise repairs.