Spark Plug Types: What They Are and How They Affect Your Engine

When your engine misfires or struggles to start, the problem often isn’t the fuel or the battery—it’s the spark plug, a small but critical component that ignites the air-fuel mixture in your engine’s cylinders. Also known as ignition plug, it’s the heartbeat of your combustion process. Without the right spark plug type, your car won’t run smoothly, even if everything else is perfect.

There are several spark plug types, mainly defined by their electrode material and heat range. Also known as ignition electrodes, they come in copper, platinum, and iridium varieties. Copper plugs are the oldest and cheapest, but they wear out fastest—usually under 20,000 miles. Platinum plugs last longer, often up to 60,000 miles, and handle higher temperatures better. Iridium plugs are the premium choice, offering the longest life—sometimes over 100,000 miles—and the strongest spark, which improves fuel efficiency and throttle response.

The heat range, how quickly a spark plug transfers heat from its tip to the cylinder head matters just as much as the material. A plug that’s too cold will foul up with carbon; one that’s too hot can cause pre-ignition and damage your pistons. Your car’s manual tells you the right heat range, but many drivers ignore it—until they hear knocking or lose power.

It’s not just about buying the most expensive plug. A 2019 study by the Society of Automotive Engineers found that using the wrong spark plug type can reduce fuel economy by up to 7% and increase emissions. That’s not just money lost—it’s unnecessary pollution. And if you’re running old or mismatched plugs, you’re also putting extra stress on your ignition coil and fuel system.

Many people think spark plugs last forever. They don’t. Even the best iridium plugs eventually wear out. Signs? Rough idle, trouble starting, poor acceleration, or a check engine light that flashes during acceleration. If you’ve never checked yours, you’re probably driving with plugs that are past their prime.

The posts below cover real-world experiences with different spark plug types, how long they actually last in Indian driving conditions, what happens when you skip replacement, and how to pick the right one without overpaying. You’ll find comparisons between brands, advice on DIY replacement, and warnings about cheap knockoffs that promise performance but deliver failure. Whether you’re driving a Maruti Swift, a Tata Harrier, or a used Honda City, the right spark plug makes a measurable difference.