Dealers Ignoring Spark Plug change intervals?

[tjkubota93]

I tend to keep vehicles forever.... 45 years ownership is the longest and my new cars are circa 2002

Have not changed a lot of plugs but my 1985 Chevrolet has benefited from plug replacement.

One of my mechanic friends said plugs are often left in until there is a problem as in drive-ability or failing State emission testing... a plug which would otherwise be simple to change can be problematic.

On the Chrysler 300 the owners manual calls for 60k change intervals... dealer said NO...

The guy who wrote the maintenance interval for that car knows more about it than the service writer............

If they could legitimately put 100k or 120k they would.

 

[N80]

I suspect the guys who write the maintenance intervals are heavily influenced by the corporate bottom line. There isn't a single aspect of car design these days that does not take into account ways in which to profit. Now, why a dealership would turn down a service job is a bit perplexing. It could be that the job is son onerous and time consuming that it isn't worth the hit to their work flow. As I mentioned, access to some plugs requires a considerable tear down.

 

[Dftodd]

We finally changed the plugs on my wife's Mazda 3 at 170,000 miles. Was actually fairly easy.

My 04 F150 never had the plugs changed on it the 10 years I owned it. When I traded it in, it had 145,000 miles and still ran nice and smooth.

 

[aczlan]

I tend to keep vehicles forever.... 45 years ownership is the longest and my new cars are circa 2002
Have not changed a lot of plugs but my 1985 Chevrolet has benefited from plug replacement.

Our '97 Dodge 1500 got new plugs and wires at around 197k miles and it went from 9MPG to 12 MPG (not sure how old they were, probably at least 8-10 years old). I was happily surprised.

Aaron Z

 

[dfkrug]

The way those ignitions worked, 2 cylinders fired at the same time and
were in the same circuit.

That's interesting. I heard the Exploder V6's shared 3 coilpacks for all 6 cyls. My '04 Tacoma does
that, too. That means there are still 3 HT wires to replace. Ugh.

I just sold my 2000 MR2, which has Iridium plugs and a 100K mi replacement interval. I had the
car for 14y and I was skeptical about such a long interval. I checked the plugs several times
in that period, and the gap did not change at all. Very impressive.

OTOH, copper plugs on our old Acura did not last more than 50K mi without getting large
electrode gaps. Modern ignitions are very powerful.

Iridium plugs are very impressive, and can be found for under $10 each if you look.

 

[Oaktree]

Now, why a dealership would turn down a service job is a bit perplexing. It could be that the job is son onerous and time consuming that it isn't worth the hit to their work flow. As I mentioned, access to some plugs requires a considerable tear down.

What he said. Especially getting at the rear plugs in something with a transverse V6. I don't care what make it is, they're all nasty to work on these days.
With the longer change intervals and aluminum heads, I'm surprised there aren't more instances of broken plugs and/or stripped threads.

 

[tjkubota93]

If they are a pain to get at, charge more. Don't turn work away.

The coils nowadays will fire across a worn plug a lot better than old cars. So a lot of times the car will run smooth until it just won't run (chrysler/jeep) or will run smooth till the coil has had enough and quits working so you gotta buy a new one (ford). A worst case scenario is a short to ground in the high side causing the coil to have excessive current draw frying the driver ckt in the pcm.

 

[kenmac]

I change pretty close to OE specs. May save me a towing trip to a garage in the middle of no where some day

 

[N80]

I've been driving cars and trucks for close to 40 years now. And some really really bad ones too (1976 AMC Jeep Chreokee). And a good many of them have had failures, breakdowns, etc. None of those was ever from a spark plug.

Now, my F150 needed a few new coils after 135k miles. Still ran fairly well but got frequent CEL. I went ahead and replaced all the coils and did the plugs since he was already in there. That was very little additional cost. So sure, if a mechanic has to be in there anyway, why not?

 

[Oaktree]

I've been driving cars and trucks for close to 40 years now. And some really really bad ones too (1976 AMC Jeep Chreokee). And a good many of them have had failures, breakdowns, etc. None of those was ever from a spark plug.

Wife had a late 90s Accord a few years back. Not sure why, but that thing was rough on plugs. 10-12k and it would start running like crap. Replace plugs, good or another 10k or so. Old plugs looked fine, but something caused them to misfire. Expensive plugs, cheap ones, all shades in between...no difference.
At least it was a 4 so they were easy to get at.