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Spark plug replacement - Kia Optima Hybrid 2012

I am considering replacing spark plugs on this vehicle myself. Every other vehicle I replaced plugs didn’t have coil packs on them, just the boots, and the plugs weren’t down in a hole. I watched a youtube video on replacement. It looks easy, but I’m skeptical. What should I watch out for?
Seized plugs and dropping the plugs are possibilities.

Make sure you don’t overtorque the plugs.Use a torque wrench for this job.

Use only the plugs specified by Kia for your engine.

A few tricks that help me. Coil-on-plug are no problem. If you can pull them without disconnecting the wires, do so. Just lay them aside. If the harness is too short, and many are, disconnect the wire carefully so you don’t break the lock.

Plug removal is easy. The spark plug socket with the foam inside will hold the plug in place. If you don’t have foam inside, take a very small piece of duct tape and wrap it over one flat on the inside of the socket. This will hold the plug enough to get it out and also install the new plug. Test it on a new plug first to make sure it holds. If it doesn’t, add more tape.

I’ve NEVER EVER use a torque wrench for spark-plugs. And I’ve yet to meet the mechanic who’s used a torque wrench for spark-plugs.

The ones specified by Kia will be plugs you buy from the dealer. Kia doesn’t make plugs…They are made for them by either NGK or Denso. Any decent auto parts store sells NGK or Denso at probably 1/3rd the price for the exact same plug at the Dealer. Use any of them.

You should!

10mm 8-12 lb. ft. 8-12 lb. ft.
12mm 10-18 lb. ft. 10-18 lb. ft.

I’ve never torqued them either

What do you do if a torque wrench can’t be used because of the location of the spark plug?

I’ve never used a torque wrench for spark plugs.


I’ll use a torque wrench for certain things . . . cylinder heads, for example . . . but generally not for spark plugs

Why? I’ve replaced HUNDREDS of spark-plugs over the years on cast heads and aluminum heads and never had a problem.


I will probably use a torque wrench, primarily because I may not have a good feel for how much to tighten. I imagine that there is practically a great deal of allowable error in spark plugs that there are not when installing a gasket.
Do you all use a thread lubricant? Or under what scenarios do you use it? The YouTube guy didn’t but I have seen recommendations, although not universally, to do so.
Oh, and I appreciate the responses.

I use to apply anti-seize on spark plugs when the spark plugs where steel going into cast iron heads.

But spark plug makers say this isn’t require anymore because of the coatings on today’s plug plugs.



I don’t use a torque wrench for spark plugs or oil drain pan bolts. I did try using one for each and both times it installed them tighter than I do. I don’t like to put a lot of stress on threads that are continually re-used. Although not a pro I have maintained a lot of cars for a lot of years going back to the days of pulling plugs every 5000 miles and 1200 mile oil changes and measuring the alcohol density in th radiator. Never had a spark plug or drain plug fall out.

Does anyone but me remember the Advertising for Kendall, the 2000 mile motor oil?

This info will be in the owners manual, and probably on an underhood sticker. Once you know the correct plugs specified by Kia, you can buy them wherever they are available.

Maybe. Some manufacturers aren’t putting the spark-plug manufacturers name anymore. Instead they are saying to buy genuine spark plugs from the dealer.

Which manufacturers? Shame on them. That will be a mark against them in my next car-buying decision.

Why ? Changing plugs is not needed that often that a simple phone call to the parts department will let someone know what plugs to use.

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Ford does this, I believe

I believe autolite supplies spark plugs for them, but you won’t find their name on the part

Actually, the owner’s manual does not have the spark plugs needed nor the gap. Haven’t looked underneath the hood yet. No big deal. I should be able to find it.

The biggest problem you may have to deal with is the plug being at the bottom of a long narrow hole. That’s the way it is on my Corolla too. I use a socket especially designed for spark plugs, which means it has a rubber insert inside. I glued that insert to the socket b/c without the glue the rubber insert tended to remain on the plug when I removed the socket. Good idea to still make sure nothing is sticking on the plug after removing the socket when installing the new plug. The other problem I had was the socket-tool extension would separate from the socket and leave the socket in the hole. I solved that by duct-taping the extension to the socket.

What else? hmm …

  • If you remove all the plugs first (which is the way I do it), make appropriate witness marks so you get the coil packs matched to the correct plug when putting everything back together, if such a thing is possible with the way it is configured. On my Corolla it is obvious how they match up by the length of the plug wires.
  • If the coil pack (or boot) seems stuck to the plug, avoid yanking on any wires to get it off. Instead try a twisting motion on the boot to break the bond, then you may have to invent some sort of prying tool to carefully pry it off.
  • Before removing the old plugs I shop-vac any debris that may be laying at the bottom of those holes, to prevent it from falling into the cylinder upon removing the plug.
  • When installing the new plug , first I double check there’s nothing been left in the hole , then I lube the plug’s threads with a very light coating of moly-lube, insert the plug into the socket, and start the threading process by hand twisting on the extension only. Don’t use the ratchet to get the plug to start threading into the head. If there’s any resistance at all,start over again. Cross-threading the plugs is something you definitely want to avoid.
  • Check the gap is correct on the new plug of course.
  • Number the old plugs as they come out. If one looks much different from the other three, you’ll know which cylinder to suspect as having a problem.
  • Even with all this pro-active-ness, sometimes something ends up at the bottom of the hole and you need to get it out. For that I have some long nosed forceps on hand. Something like this.
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