Fasteners are everywhere in a car. After all, they hold the thing together, and a typical vehicle contains thousands of them. But because a car is a heavy, moving machine, they’re subject to constant heat, pressure, and vibration. Some of them end up rusting, fusing, or seizing together as a result. That’s why anti-seize exists, specifically to prevent any of that from happening.

Anti-seize is a special compound that goes onto threaded fasteners and other metal parts that touch each other. It’s basically a thick grease, but while actual grease is just thickened base oil designed to lubricate, anti-seize is more of a paste packed with microscopic metal particles.

When applied for the first time, anti-seize is wet, so it acts as a temporary delivery system that helps install the part. Once things get hot, though, the grease cooks off permanently and all that remains is the crushed metal particles. Those are what stop the threads from fusing together.

Beyond this, the paste also helps fight galvanic corrosion, a process that happens when two different metals get cozy in the presence of moisture. A common example is a steel bolt threaded into an aluminium housing. Without anti-seize, you get oxides building up, parts swelling, and a fastener that’s basically welded in place. This just goes to show that protecting your car from rust goes beyond just keeping the paintwork looking nice. The sweet spot for applying anti-seize is anywhere two dissimilar metals meet or anywhere you’ll probably be unbolting things down the line, but this type of lubricant is not really a fix.

Keep in mind that anti-seize will not work on anything that’s already seized up, so the best time to apply it is during routine maintenance, when you have a corrosion-prone fastener apart in your hand, not after the damage has already started. 

As mentioned before, anti-seize should be applied in a spot where two different metals meet.That basically means suspension fasteners, underbody tray bolts, exhaust hardware, brake caliper bolts, and battery terminals. Engine head bolts are another spot some technicians swear by.

How you apply it matters just as much. A thin coat on the threads is plenty, and you only want it on the part that ends up hidden inside the nut or housing. Smearing it across the exposed bits of a component is a quick way to invite dirt and grit to stick around. Once you’re done, drop your torque value by roughly 20% to 30% too, and it would also be a good idea to follow the 20% rule for torque wrenches, since anti-seize has a lubricating effect, and you don’t want to overdo it accidentally.

There are also places you should avoid using anti-seize altogether. Lug nuts are a hard no, since the slippery coating makes it way too easy to over-clamp when you’re installing a wheel. Doing so can warp brake rotors, stretch wheel studs, or in the worst case, even let a wheel work itself loose, which you certainly don’t want to happen on the highway.

Then there are spark plugs. Seized spark plugs, the ones that fuse to the cylinder head and refuse to come out, are a genuine pain to deal with, so the instinct to coat the threads for better lubrication makes sense. The catch is that most modern plugs already ship with a corrosion-resistant nickel or zinc coating on the threads, and slathering anti-seize on top of that can void your warranty. 

Finally, a couple of other quick skips. You’ll also want to leave brake caliper slide pins alone, the small bolts that let the caliper float in and out as you brake. Those need high-temperature brake grease instead so they keep sliding smoothly under heat. Of course, if a thread is already chewed up, no compound is going to save it, least of all anti-seize.