When to change spark plugs - relatively high-spec engine

[NMNeil]

Evoluzione said:

My personal preference with plugs is that they do a heck of a lot of mileage before being problematic, when they start to cause misfires or poor running then change them, changing them early is a waste of time and money.

That's like saying don't change your brake pads until the car won't stop anymore.

[NMNeil]

Boosted LS1 said:

Not so. It depends on the plug. You need to have a good earth.

It depends on if you want the plugs to come out easily or if you the threads in the head to strip.
Oh, and the anti seize I use contains copper, which is highly conductive.

[kambites]

Do plugs actually seize if they're torqued correctly? I've certainly have found mine to be remotely stiff when I've come to change them and I don't put copper-slip or anything on them. I tend to replace mine every four years (when I'm taking them out to make changing the cam belt easier anyway) and I often struggle to tell the new ones from the old ones after that period.

But then I can get a full set of decent plugs for my car for ~£25 so it's a no-brainer to replace them really.

Edited by kambites on Sunday 28th June 13:54

[anonymous-user]

The main reason not to apply any form of lubricant to something that's supposed to be assembled "dry" is the torque will be completely wrong - probably significantly over-tightened.

If you're worried about plugs seizing just whip 'em out, wire brush the threads (if needed) and put 'em back with the correct torque. Gives you a chance to look at the condition of the tips along the way.

Do I do this? No. Some of the plugs on my current cars can only be accessed by a highly-trained octopus, so I just leave 'em in until I think it's time to change them.

[Boosted LS1]

NMNeil said:

Boosted LS1 said:

Not so. It depends on the plug. You need to have a good earth.

It depends on if you want the plugs to come out easily or if you the threads in the head to strip.
Oh, and the anti seize I use contains copper, which is highly conductive.

Modern plugs already have an anti-seize plating on them. You don't need copperslip unless you have old plugs with black threads.

[dhutch]

I've not had plugs seize, or always stuck religiously to the service intervals, but I've also never taken the piss or left them until they fail.

[NMNeil]

kambites said:

Do plugs actually seize if they're torqued correctly? I've certainly have found mine to be remotely stiff when I've come to change them and I don't put copper-slip or anything on them. I tend to replace mine every four years (when I'm taking them out to make changing the cam belt easier anyway) and I often struggle to tell the new ones from the old ones after that period.

But then I can get a full set of decent plugs for my car for ~£25 so it's a no-brainer to replace them really.

Steel fittings, including spark plugs, suffer from galvanic corrosion, and tend to 'weld' together.
Champion even sell their own anti seize.
https://www.aircraft-tool.com/shop/detail.aspx?id=...

[Boosted LS1]

Great, I'll go and buy some then because being Champions I know I'll be removing them on a regular basis. Maybe they don't have quality thread coatings or have spotted a commercial opportunity?

NGK have been my preferred plug for years and NGK say this:

https://ngksparkplugs.com/en/resources/5-things-yo...

also, lots of threads like this:

https://www.driven2automotive.com/blog/why-you-sho...

I to used to grease the threads but have stopped doing it even if I still feel I must :-)

[Zener]

I wouldn't use Champion to break a window personally you can use an anti-seize lubricant just dont go silly a small smear on the threads is all thats needed treated or otherwise anyone that states their plugs come loose because of, or heat transfer blah blah is just talking bks and should not be let loose near anything mechanical , your choice really