Should I Add Anti-seize to Car Bolts?

I started working on cars prior to the information age boom. I picked up the practice of adding anti-seize to my fasteners, but I wondered why the manufacturer didn't. Could it mean I would have a problem literally down the road?

-Sean J. Miller 12/28/2023

I started working on cars as a teenager back in the late 80's.  Of course, being a broke kid, that meant I was working on vehicles from the 70's.  One thing I noticed was that the manufacturers did not use thread lubricant.  Datsun's were awful to get things apart due to rusted and "frozen" fasteners.  Impacts, torches, and even just drilling out a bolt was common place.

So, all the way back then, I elected to use anti-seize on all threaded fasteners.  For the life of me, I can't remember what made me start.  I think my dad had a little jug of the stuff.  Perhaps, I fought something that kicked my butt, so I said "never again!"  However, for the early years, I had reservations on applying it, especially in vibrating and rotating services such as on wheel studs.

I did some big jobs over the years and spent just about every Christmas break doing some major refurbishments including engine head rebuilds, torque converter replacements, and full suspension overhauls. I've maintained 3 vehicles so far to the 250K+/25 year milestone. So, after all these years, what did I find with anti-seize performance?

Well, first, let's talk about what anti-seize is.  There are two types commonly found at automotive stores.  Grey and Copper.  The grey is nickel based for most automotive applications.  The copper is for where things get really hot such as around the engine and exhaust.  If you use nickel in exhaust service, it smokes off, so Copper is preferred.  Otherwise, just having grey around is great.  Both have flakes of metal and a petroleum (grease) base.  So, you have to be sure not to get it into places like a piston cylinder or the metal flakes will cause scoring to the surface.  In turn, don't use it as a lubricate for things that slide like brake components. Last, you have to be careful not to get it on you as nickel is actually very toxic.  It tends to stain and get on everything if you are sloppy with it - so where gloves and take care.

So, what did I learn over the years?  For one, I learned in the Oil & Gas and chemical industry that all piping flange fasteners expect lubricant used liberally - even on the back of nuts and on washers.  They have a calculation for torque that includes a "nut factor" that depends on all contact surfaces being well lubricated with anti-seize.  So, that gave me confidence that using it on an automobile is definitely a preferrable practice if you want to keep a vehicle for years.

So, now for over three decades, I put it on everything threaded- including spark plugs and wheel studs (lug nuts).  I just put a tiny, thin layer on spark plugs to be sure not to get it into the cylinder head. I did this because I had a spark plug without it seize in the hole and it was a terrifying experience.  I never had a wheel lug nut come loose or trouble with a spark plug again.

Many repair scopes I only do every 8 years or more throughout the 30 year life of a car like front wheel hubs, exhaust manifolds, and brake caliper replacement.  When I went back in for round 2 (and 3) on them, the anti-seize was very much present and looking fresh.  I've even simply reused the fasteners that were buttered up 10 years ago without adding any more lubricant. I never need a torch or impact driver to loosen an anti-seized fastener.  Just a wrench and rubber mallet to help it start without any strain on me.  After a fastener initially breaks, within a couple of turns, I can remove it the rest of the way just with my fingers!  No galling on the way like with an un-buttered bolt.

When I apply it, I first wire brush the threads.  If a fastener was in bad, rusty shape, I use a Dremel with a wire wheel to make it shiny like new.  I then butter it up fully, just as I was trained in the Oil & Gas industry - covering all contact surfaces including the bolt head face and washers.

Some sources say to increase the torque spec by 25% when you apply anti-seize.  This may be true in the automotive industry, but I don't.  That's because I know that in the awkward angles you have to tighten fasteners in a vehicle, I always over-torque inadvertently anyway. I learned this firsthand with a flange torque training prop that had strain gauges installed on bolting.  That little final extra pass one does for "good measure" - especially if doing it by pushing down versus pulling up, gives a significant peak of torque.  Torque charts in oil & gas already include the nut factor the lubricant applies, too.  After decades of doing this, I've never had a water pump leak or a vacuum problem because I antiseized and didn't increase the torque setting on the torque wrench.  However, I have pushed out a rubber gasket on a transmission pan due to intentionally increasing the torque spec thinking I'd be doing myself a favor.

So, in all, based on over 3 decades of first hand, multi-car experience - I encourage my son Connor to absolutely apply anti-seize to automotive threaded fasteners.

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