Anti-Seize on Spark Plugs: Good Habit or Bad Idea?

People ask nearly every day whether or not they should use Anti-Seize on Spark Plugs. Is it a good idea? Is it a bad idea? The answer isn’t really that straightforward. Read on to learn more!

Anti-Seize on Spark Plugs: The Facts

In decades past, it was a good idea to keep a bottle of anti-seize around for when you needed to change spark plugs. You’d carefully brush a small amount into the bare metal threaded section of every new spark plug before installing it into the engine so that they would come out easily when it was time to replace them.

Today, times have changed. Spark Plugs are thinner and lighter. The bodies have a bright, shiny plating rather than bare, dark iron. This shiny plating serves two purposes. One, it helps prevent the spark plug from rust and corrosion, which helps them to not get stuck in the engine in the first place. Two, the plating actually acts as a release agent and separates from the plug body when you remove the spark plugs from the engine. Basically, it does the same job as antisieze, so adding Anti-Seize on top of it is unnecessary.

Additionally, Anti-Seize makes the threads “extra slippery” (there’s a more technical description, but “extra slippery” works well enough), which will alter the actual torque applied by up to 25%.

For example, it’s a spark plug’s required torque is 100 in/lb, and you set your torque wrench to 100 in/lb. You then torque a spark plug lubricated with Anti-Seize. The actual torque on the threads could wind up as high as 125 in/lb. Since modern spark plug bodies are thinner and lighter, and modern cylinder heads are often made of aluminum, this could potentially cause a number of problems.

When Should You Use Anti-Seize?

According to our staff of auto mechanics, You should use antisieze on spark plugs that have a dark iron (not nickel plated) body. You also probably want to use it if you remove a plated spark plug, and plan to reinstall that same spark plug. The rest of the time, it’s best to leave the Anti-Seize on the shelf.

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