Our car experts choose every product we feature. We may earn money from the links on this page.

Are your spark plugs due for a swap? Here’s how to change them quickly and efficiently, with tips from an expert.

Spark plugs are an essential part of your engine’s operation. When your engine fires, it’s the spark that causes the ignition cycle to begin. Over time, spark plugs wear out and should be replaced. If your car is in need of a fresh set and you plan to do the job yourself, you’ve come to the right place.

Road & Track spoke with Kevin Hines, senior technician at McLaren Philadelphia, to learn the correct way to change spark plugs efficiently and safely. Hines is North America’s only factory-certified McLaren F1 technician, which means his day job is working on $20 million exotics. If anyone understands how to swap out plugs, it’s him.

Before reading any further, we suggest consulting your car’s owner’s manual for exact instructions on how to change spark plugs on your car. The manufacturer’s suggestions may differ from the instructions below.

Depending on which car you drive, there can be dozens of different spark plug brands to choose from. It’s up to you to pick the right one. For most cars, Hines highly recommends buying a set of plugs straight from your car’s original manufacturer. These are the plugs originally designed to work with your motor. If you want to save some cash, buy a set from the OEM’s supplier.

You’ll also want to make sure the spark plugs you buy are gapped correctly. “[A spark plug’s gap] is crucial to how an engine is designed to run,” Hines tells us. “Every engine is different, so find your manufacturer’s specifications and learn how to gap spark plugs.”

Gapping spark plugs might sound scary, but it’s actually simple. Gapping tools are easy to use, and can be bought online or at any auto parts store. Even if your plugs come “pre-gapped,” we suggest using a tool to check and make sure. You can never be too careful—this is your engine, after all.

If you happen to accidentally drop one of your new plugs? Simply discard it and get a new one, says Hines. “You can have hairline cracks in the ceramic and that’ll cause all kinds of problems that’ll take forever to figure out [after they’re installed],” he says.

At minimum, you’ll need a handful of simple tools to swap out your plugs. A ratchet, a couple of extensions, and a specialized spark plug socket will be supremely helpful in making the removal and installation of your plugs easy. The socket can be found online and at most auto parts stores for an affordable price. If possible, we recommend also having a torque wrench handy.

If there are accessories or trim pieces in your engine bay in the way of spark plug access, make sure you have the tools to remove those as well.

Once you have all of the tools you need and the replacement plugs handy, figure out how you’re going to access your car’s spark plugs. Many modern vehicles often have cosmetic trim pieces or things like air intake boxes, coolant overflow tanks, wiring, windshield washer fluid tanks, or other items in the way. After you’ve solved that issue, you can move onto the wires.

Most spark plugs get their electricity through either plug wires or coil packs. With wires, the current travels from a shared coil pack that usually powers all of the cylinders. With coil packs, each cylinder has its own individual coil, which sits on top of the spark plug. No matter which setup your car has, you’ll have to remove them to get to your plugs. On some cars, the wires or packs can simply be pulled out by hand. Others are sealed with rubber grommets or held down with screws or clips. It’s up to you to figure out how your car is designed to get access to the plugs.

After you’ve done that, you can finally get at the plugs themselves. Before taking a socket to them, we recommend vacuuming the area, including the recesses where the spark plugs sit. You’re about to open up holes directly into your cylinders, remember. The last thing you want is for debris to sneak in after you remove the plugs.

Extracting the plugs is as simple as extracting any other hex bolt. Once you have the correct socket, you’ll likely need an extension, depending on the position of the plug in relation to your engine’s dimensions. If they were torqued correctly by the previous installer, they should break loose with little effort. After you get the plugs out, inspect them. Look for signs of oil buildup, unusual wear, or darkening. The condition of your plugs can give you an indication of how your engine is running.

Now you can install the new plugs. Make sure to thread them in by hand; the last thing you want is to damage the threads on your engine. When tightening plugs, we highly recommend using a torque wrench to eliminate user error. But torque wrenches are expensive, so if you don’t have one, that’s okay. You can get by through feeling out when the plug bottoms out on your cylinder head, though we implore you to be extra-cautious. Over-tightening a spark plug on an aluminum head can severely damage the threads.

Once the new plugs are installed, you can reinstall the wires (or coil packs, if your car has them). Hines recommends dabbing a bit of dielectric grease in between where the plug connects to the wire to ensure a solid electrical connection, just to be safe. “And then make sure you feel a positive engagement, especially on spark plug wires,” Hines adds. “Make sure you can click on and feel the connection.”

After the wires or coils are fitted, you can reinstall any trim pieces or other objects that were previously blocking you from accessing the spark plugs. After you’ve done that, start up your car to see if it runs smoothly. If it does, congratulations, you’re done!