100K miles: need to replace spark plugs?

[Benzadmiral]

My venerable '03 Buick Park Avenue, 3.8L NA engine, is coming up on the big milestone: 100,000 miles. I figure another week at my usual driving routine. Perhaps I'll take a pic of the odometer if I can. Anyway, there will be things to do and replace; oil change in January, it may be time for the tranny fluid, etc.

However, one thing the manual mentions is changing the plugs at 100K miles. I have no problem with doing it; like a lot of you, I remember having to switch plugs every year or two in '70s and '80s cars, so 10 years seems like science fiction come to life. But the Buick's gas mileage is the same as ever, and it drives as superbly as always. Is this 100K marker a preventive maintenance item? Or did GM expect that most cars by this time would be showing evidence that the plugs are really degraded?

Not trying to skip the job. I'm just wondering, if the fuel economy and driveability are unaffected, if there is any reason I can't wait a month or two.

 

[Thax]

Go ahead and change them. Use AC Delco 41-101 plugs and go another 100k. The reason they spec 100k is that the OEM plug is a Iridium plug and the general service life for this plug is 100K. You can easily wait a month or two just eventually do it. Just make sure to grease them up real good with dielectric grease.

 

[beechcraftted]

I replaced the plugs at 100K in the wifes' 3.8 Gran Prix. It still ran perfectly and mileage was good, but several of my car buds warned that if I left them in longer, they may become impossible to remove at a future date when it was really necessary.

I say just replace them @ 100K with some good double plats and sail on for another 100K.

 

[PhillyJoe]

Might as well change the plug wires while you're in there as they also have 100,000 miles and may be nearing the end of their service life.

 

[HTSS_TR]

Originally Posted By: PhillyJoe
Might as well change the plug wires while you're in there as they also have 100,000 miles and may be nearing the end of their service life.

If 100k miles is the life of plug wires then my LS400 with 300k miles should have plug wires changed 3 times already(100k, 200k and 300k), but it still has original plug wires without misfired.

 

[Corvette Owner]

Yep, today's high voltage ignition systems coupled with platinum or iridium plugs equals one very long service period.

I took a set of irridium plugs out of my daughter's Chevy Malibu at 110,000 miles (recommended period) and was surprised how good they looked, they looked new !

I have used double or four post platinum's in the past, but now will use irridium in all my cars. I replaced my Murano with iridium's.

 

[fdcg27]

I'd replace them in the next couple of months when covenient.
They are probably still pretty good, but if the gaps grow enough, you can end up replacing the coils as well.
Also, if you leave them in long enough, they can become very difficult to remove, although this is an iron engine, so it should be possible to get them out without damaging the threads in the heads.
I'd go ahead and replace the wires as well.
You'll then be good to go for as long as you'll own the car.

 

[jjcom]

I'd go a head and do it...they're not too bad to replace on those cars. Those engines bays give plenty of room (for a FWD at least) to get to the plugs. I've had great luck using AC Delco plugs or Autolite XP plugs. Both seem to offer great service, I just pick the one I can get the cheapest at the time.

For plug wires, I normally grab a set of Autolite Professional series wires. Knock on wood, on all the cars I've put a set on, I haven't had one problem.

 

[Propflux01]

Yes, change them. they are worse off than you think.

 

[G.Frost]

Spark plugs are a 'preventative maintenance' item; You want to replace them before any kind of misfire or other failure, otherwise you could cause problems with Catalytic converter, sensors, ignition system, deposits, etc. Ideally they will still be working as new when you replace them.

 

[HTSS_TR]

Originally Posted By: Corvette Owner
Yep, today's high voltage ignition systems coupled with platinum or iridium plugs equals one very long service period.

I took a set of irridium plugs out of my daughter's Chevy Malibu at 110,000 miles (recommended period) and was surprised how good they looked, they looked new !

I have used double or four post platinum's in the past, but now will use iridium in all my cars. I replaced my Murano with iridium's.

I changed E430's 16 plugs when it was 7 years old 8x,xxx miles, the recommended is 5 years/100k miles. The plugs look new too, If I took one out to check before I bought 16 OEM plugs, I would put it back in and drive another 80k miles.

 

[InvalidUserID]

You won't be HURTING anything by changing them out and likely aren't gaining much by holding out an additional X days/months.

I'd change them. Sounds like you aren't having any drivability issues but why wait for those?

 

[bvance554]

I have 126,000 on my Subaru and I have yet to pull a spark plug. I'll get around to it one of these days. But they just keep on trucking, with no change in efficiency.

 

[SteveSRT8]

Why change them? Modern cars will throw a code at the slightest hint of misfire. That's when you need new plugs.

Some imports have notable issues with coil drivers going out that may be aggravated by resistance but plugs can last a LONG time these days!

 

[Benzadmiral]

Early next month, then. I certainly don't want to wait for driveability issues, and I sure don't want to have them freeze to the block. Should I stay with AC Delco, and the OEM-style wires, or is there something better since 2003?

 

[NateDN10]

I've heard that AC Delco's are now re-branded NGK's.

Either way, AC Delco, NGK, and Denso are all known for good reliability without gimmicks. Pick whatever has the proper cross-reference for the best price!

 

[KrisZ]

Originally Posted By: G.Frost
Spark plugs are a 'preventative maintenance' item; You want to replace them before any kind of misfire or other failure, otherwise you could cause problems with Catalytic converter, sensors, ignition system, deposits, etc. Ideally they will still be working as new when you replace them.


Yep, I wouldn't wait for a problem or a code to show up before changing the plugs, because that means you have to do it right away or risk damaging components.
100k is a good interval that gives you plenty of leeway to do the job. It doesn't mean you have to do it exactly at 100k mark, but you should look for a good opportunity to do the job.

I take the same approach for other items as well, like brake jobs. I don't wait until I hear metal on metal grinding to take a look at them. I inspect them at each tire rotation and when they're close to being used up I shop around for good deals and have parts ready ahead of time. Then I just wait for a nice warm weekend or when I have time to do the job and just change them.
If I wait till last minute I may not have the luxury of doing the job on my schedule and will usually have to compromise something else for it, like family time, day at work or doing something around the house.
To me this is more important than getting the last bit of life out of a component. In fleets, that's a different story.

 

[hattaresguy]

I wouldn't waste the money, wait until you have a misfire.

I think your 3.8 uses cast iron heads, in that case disregard all the aluminum head guys saying you won't be able to get them out, you will. Just use a bigger wrench.

I bet you would get over 200k before one of those plugs threw a code.

On GM engines with cast iron heads wait for a misfire and save your money, chances are it won't happen during your ownership.

 

[sciphi]

Use Delco iridium plugs and call it a day. Unless your mechanic can get the NGK iridium plugs cheaper, which is who supplies Delco these days.

The rear bank will be a bit of a minor bugger. The OEM's had these metal boots on them that can cut fingers when trying to get the plug wires off. If you tackle those first, the front 3 will be cake by comparison. Best way is to lay across the engine, and don't knee the vac hoses on the front side.

 

[rjundi]

For those folks who like waiting for flashing CEL: