PSA: The Right (and Wrong) Ways to Handle Iridium Spark Plugs

For the vast majority of vehicles on the road, swapping out spark plugs is gravy work. Yoink the old plugs, make sure the replacements meet the necessary gap spec, install the new plugs, and button up the ignition system. You’re in and out of there in no time, right?

That may have been acceptable back in the days when practically every vehicle used good ol’ copper core plugs that didn’t care too much about how they were handled or adjusted. Accidentally set the gap a few thousandths off? No biggie, just bend the strap again and verify with your gauge. Easy peasy.

But new techs and DIYers alike should know that the game has changed. Those old methods can create new problems in a hurry, leading to comebacks, driveability issues, and other headaches. And it all comes down to one of the rarest metals on Earth: iridium. Ironically, it’s also one of the most common core materials found in modern spark plugs.

While manufacturers spec spark plugs with iridium cores for a few reasons, they are broadly used to squeeze performance out of optimized engine designs, often supporting additional technologies like forced induction, direct injection, and sophisticated ignition systems. So don’t be surprised when you see one, and definitely do not make any of the following rookie mistakes:

• Don’t touch the electrode. Iridium is brittle, and it doesn’t take much to ruin an electrode.
• Don’t gap iridium plugs. They are preset at the factory. Simply order the correct plugs from the get-go, and you won’t need to touch your gauge set.
• Install iridium plugs with care. That goes double for modern engine designs that position the plug deep in the engine to accommodate direct injection. Dropping a plug down a spark plug well can damage the electrode, and if you install that plug, the vehicle may exhibit ignition issues.
• Related to the point above: make sure your spark plug sockets are in good condition. Most spark plug sockets will have a little rubber ring inside to help hold the plug as you install it. If that donut is worn out or missing, you’ll run the risk of dropping the plug mid-install.
• It is possible to clean deposits off of iridium plugs, but only a soft brush and isopropyl alcohol should be used. Don’t reach for your wire brush, and absolutely do not use any abrasives. Heavy deposits on a fresh plug requires diagnostic work, or the deposits will probably return quickly.