Spark plug replacement questions

Hi there fellas

I have a couple of questions I hope you guys can help me regarding spark plugs and wires.

I had some time today to replace the three of the six spark plugs on a 2007 Mazda 6 S V6 3.0L.

The plugs had some sort of clear paste around the ceramic part and on the “tip”. I am wondering what is this? The Haynes manual doesn’t mention anything about it, only to apply anti seize on the threads.

I have seen Scotty Kilmer put “Electrical contact grease” and some people mention putting dielectric grease on the boots. Are these the same?

The Haynes manual says to put anti seize but I have read that you shouldn’t put any anti seize because most spark plugs nowadays comes coated. The spark plugs I bought are Iridium IX: TR5IX 7397. It has a “chrome finish” on the threads, so I just installed them like that and torqued it to 11 ft lbs.


Triathlor, that’s no doubt dielectric grease inside the plug boots. That’s not a bad idea to use it there. Many/most technicians I know of do that.

I take it those plugs are “factory” specified parts? If the other plugs (original?) came out okay without anything on them then I would do just as you have done, apply nothing to the threads.

I always use the factory specified plugs (brand / heat range / part number) in any vehicle I own.
CSA :palm_tree::sunglasses::palm_tree:


I’m pretty sure you don’t need anti seize on those plugs, the plating acts as an anti seize. I use it on cheaper copper plugs usually. I don’t know what the paste is on the electrode, perhaps you’re supposed to wipe it off. If you’re using new wires, they almost always come with dielectric grease already in the boots. If your old boots are dry, you can put a dab of the grease in them.

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… anything else is an experiment, unlikely to yield benefits that outweigh unwanted side effects.

So electric contact grease and dielectric grease are the same thing? I will go get some dielectric grease today. I read a Cartalk article/interview where they were talking about the ceramic portion of the plug braking when taking the boot off after years of use without dielectric grease.

Car has 155k miles. So the car already had the plugs changed at the dealership. There is also anti seize on the threads but the plugs are already coated.

The owners manual specifies another brand of plugs but I bought the same I found in the car by coincidence.

Install the plugs that are listed in the owner’s manual . . . NOT the ones that the previous guy happened to install. Could be that guy installed whatever he had laying around.


I believe contact grease is the same thing just another name. I think the main concern with using anti seize is it changes the torque value from it lubricating the plug. A lot of the regulars here use the same factory brand plugs to avoid problems. If you used the correct plug and gap and they aren’t causing problems, I wouldn’t worry about changing them all again.

Yeah you can use the dielectric grease in bulb sockets etc. to prevent rust and provide a good contact. I also used it on my TV signal booster.

The way OP wrote it . . . it’s not at all clear if he used the plugs specifically called for in the owner’s manual, or if he just installed what the previous guy did, which may or may not have been correct

I also use it often on household bulbs to prevent seizing (galling) that causes the bulb bases to freeze in the sockets.

Yeah, I too suspect it’s dielectric grease on the boots. .

Lol, I don’t know, he said it was a coincidence though. Hopefully he looked up the plugs for the car first and didn’t just get what was in there.

The way OP worded it is not crystal clear, in my opinion

Until he specifically says he installed the plugs called for in the manual . . . I have some doubts

pay for the big tube, you’ll never need to buy another one for years, if ever.

I do, too. It seems that when bulb bases and sockets were made of brass there wasn’t a problem. Now, since most bases and sockets are made from cheap aluminum that’s where I have had problems with the two seizing. The old brass-on-brass combination was a more “slippery” combination, whereas aluminum-on-aluminum is more “grippy.”

I have some recessed fixtures where you can’t grip the sides of the bulbs and without grease they can be nasty.

On our “new” condo I changed all the bulbs over to LEDs. The energy savings and reduced heat out-put are amazing! I hade one bathroom fixture with eight 40w incandescent bulbs, that’s 320 watts and when the switch was on you could actually feel the heat. I replaced them with eight 60w equivalent LEDS using 5 watts each, that’s 40 watts total now and they’re so cool you can grab onto them after them been on a while and they are just barely warm.

Moreover, I’m not expecting to have to change any bulbs for a long time. Additionally, I’m sure the A/C will not be wasting energy trying to make up for the old bulbs’ waste heat and the whole project should save on my FP&L monthly bill.
CSA :palm_tree::sunglasses::palm_tree:

If your Mazda’s still purring a month from now, you’re probably good to go…


You can get “socket lube” at the big box stores like Menards. Its more of a paste than the dielectric stuff but suppose its similar. It’s only a couple bucks but works well on particularly those small candle abra bulbs that tend to stick. Even with the power off, I don’t like going at them with a pliers, and would never waste a potato on one. Speaking of engines, getting zapped with 20,000 volts is no fun-goes right up your arm, so I tend to respect and fear electricity.

I am sorry for replying now. I was very busy. I have taken the plugs and added the dielectric grease.

The manual calls for Motorcraft AJ57-18-110 spark plugs or equivalent. I can’t find the specs for it so I don’t know what the equivalent is. When I went to Autozone for some spark plugs they recommended the NGK TR5IX. Every website says that it is an exact fit for the vehicle.

I compared the ones on the vehicles and since they matched to the ones in the vehicle I proceeded to install them. The car runs fine.