Spark Plug Replacement Intervals - Why?

[Auto tech]

Where did I say that I didn’t want to do it? I asked for someone to clarify what the potential failure mode effects of eroded spark plugs are. All I got was a bunch of ways of saying because the manual says so until one person bothered to actually address my question. Since then the thread has turned into practically all condescension and strawman comments about how I must not do any maintenance.

For a site that’s supposed to be about helping people understand how things work, there seems to be an awful lot of gatekeeping against anyone who asks the wrong question.

Like I said I meant no offense. It doesn't seem like you are taking the advice that was given. Maybe you are I don't know? It's a touchy subject for all of the technicians on here I'm sure. We have seen what happens when customers do not keep up with maintenance. It ends up costing them a lot more than if they just did the maintenance. Had a customer years ago burn a valve and trash the cats from not replacing spark plugs. Another common one is engines destroyed from not doing timing belts at the correct intervals. Have a good day

 

[leeharvey418]

It doesn't seem like you are taking the advice that was given

Really? Because there’s a response by me on the first page where I thank SC Maintenance for giving me a legitimate answer. Since then, it’s been nothing useful.

 

[Auto tech]

Really? Because there’s a response by me on the first page where I thank SC Maintenance for giving me a legitimate answer. Since then, it’s been nothing useful.

I like how you edited that one sentence out of the whole response. I'm not going back and forth with you over this. Have a good day

 

[ATex7239]

I had the ceramic insulator on an old set of plugs get brittle and crack from age/heat once. On one of them a piece broke off and almost fell into the engine during removal. I caught it. But man that would been a nightmare to deal with. I don’t run plugs out after that experience; before or at the recommended interval only.

 

[BMWTurboDzl]

Yes of course but without that use VW on these engines is 40k mi and I'd follow it. Atlas VR6 is 60k and changed those earlier this year. Focus is 100k. W8 is not sure but I had them changed when I got it.

BMW M5 (F90) is 25k miles. Yikes.

 

[ammolab]

My Chevy LS3 V8 ran great at 70,000 miles. My son had the same car and just changed his plugs @ 95,000 miles per the maintenance listings. They looked BAD! So I took mine out. Also BAD! Most had huge gaps and 4 pretty much had no center electrode at all. Pic is one of the worst ones and a new plug. I’m changing this new set @ 50,000 miles or sooner.

 

[Nick1994]

It isn’t even worth the discussion on a 4-cylinder IMO. 10 minute job.

Now on a car that you’ve got to pull the intake manifold and a bunch of other stuff to do it? Let’s talk.

 

[kschachn]

Where did I say that I didn’t want to do it? I asked for someone to clarify what the potential failure mode effects of eroded spark plugs are. All I got was a bunch of ways of saying because the manual says so until one person bothered to actually address my question. Since then the thread has turned into practically all condescension and strawman comments about how I must not do any maintenance.

For a site that’s supposed to be about helping people understand how things work, there seems to be an awful lot of gatekeeping against anyone who asks the wrong question.

Such a conclusion may be forgiven considering the thread title is:

Spark Plug Replacement Intervals - Why?​

 

[KrisZ]

Have they been changed yet?

 

[Arc]

I ran a plug for so long in my Polaris scrambler that it burned the end off of the ground. I would say it's a safe bet that you should change your plugs when they start to burn up. But if you clean them and adjust the gap they will last a long time.

 

[Davejam]

Again - I see no drop in mileage. This would obviously be the first indication of electrode burn-back, and it doesn’t seem to be happening.

I have a degree in mechanical engineering. I get that things wear out - but I also know that they give indications that they’re wearing out. I don’t accept replacing a widget that’s still fully functional just because somebody put a replacement interval in a manual.

How would you know you see no drop in mileage versus ideal case? There's so many variables here, the only way to know would be a very well controlled study which is not practical.

As a mechanical engineer you should understand that you replace things before failure to avoid catastrophic or unplanned failure.
Preventative maintenance, if you will, is the hallmark of any mechanical integrity program.