VW's 40K Plug Interval: The Result of Doubling It

[The Critic]

I have a former manager who owns a 2005.5 VW Jetta with the 2.5L 5-cylinder engine. The car calls for a 40,000 mile spark plug replacement interval despite being equipped with double-platinum, NGK PZFR5J-11 plugs from the factory.

I told her to change the plugs a long time ago, but I finally got around to doing them for her earlier today - at 80,000 miles - which is double the recommended service life. The owner never had any driveability complaints with this car.

So ladies and gentleman, this is what happens when you run the plugs for twice the recommended interval:

Up close of one plug:

Not too bad, IMO. Is it a good idea? I don't know, you tell me.

I replaced the plugs with a fresh set of NGK PZFR5Q-11. Why? Because NGK said this is now the proper plug, so perhaps there was an update. If anyone has any info on the differences between the J and the Q, I would be very interested in hearing it.

Oh, and the plugs were pretty crusty when removed and made quite a bit of noise, but came out smoothly and easily. New plugs were installed dry and torqued to 18.5 ft-lbs as per VW's specifications.

 

[The Critic]

Spark Plug part # breakdown for NGK:

http://www.ngksparkplugs.com/techinfo/spark_plugs/partnumberkey.pdf

 

[AstroTurf]

Wonder what the MPG difference was?

 

[fdcg27]

That plug looks pretty good.
How much had the gap grown over 80K?
You can still see the platinum button on the ground electrode and the center electrode still looks pretty good.
I wonder whether the 40K recommendation arose from concerns about difficulty in removing the plugs without damaging the threads in the head?

 

[229]

"Is it a good idea? I don't know, you tell me."
"BITOGer: an individual who enjoys playing Russian Roulette with their vehicles because they cannot stand being told what to do by the manufacturer."

Ever check the price of the ignition coils? Makes plug replacement seem like a bargain. Just saying...

 

[hate2work]

Originally Posted By: 229
"Is it a good idea? I don't know, you tell me."
"BITOGer: an individual who enjoys playing Russian Roulette with their vehicles because they cannot stand being told what to do by the manufacturer."

Ever check the price of the ignition coils? Makes plug replacement seem like a bargain. Just saying...


This isn't the OPs car, and he tells us that he told the car owner to change them much sooner. Clearly this is not a good idea, IMO.

 

[Bottom_Feeder]

Originally Posted By: 229
"BITOGer: an individual who enjoys playing Russian Roulette with their vehicles because they cannot stand being told what to do by the manufacturer."

 

[Bgallagher]

Originally Posted By: AstroTurf
Wonder what the MPG difference was?


Probably slowly dropped. Not enough for the customer to realize. Kind of like when you lose some weight. People who see you everyday wouldn't notice but somebody you see every other month would notice (nice when they do haha.)

Those plugs look well worn. Not as bad as I expected but I don't mess around with plug changes. Do it how the manual says it. Not worth the issues worn plugs can cause. in terms of wear and ineffeciency

 

[bepperb]

I thought everyone specd plugs for 100,000 miles or more? There's no reason that same double platinum plug wouldn't be in the engine for 100~120,000 miles if it was an American or Japanese car.

They look decent to me. I'd be surprised if there is a big mileage difference, but at the same time you'd need to compare the gap to the new to say.

 

[punisher]

Agree, they don't look that bad to me. Whether or not the increased gap/voltage requirements will kill a coil faster is a valid question.

 

[Hokiefyd]

They look good. The platinum pads on the ground electrodes are still there. Gap is hard to estimate from pictures, but they look pretty good. Could be re-gapped and re-installed and pushed for some more miles, but if it were mine, I'd have changed them as well. A 40,000 mile interval on dual-platinum plugs is awfully short. The shortest interval I've otherwise seen given for dual-plat plugs is 75,000 miles (Chrysler 3.x V-6 engines).

 

[rjundi]

My brother never changed them on his 2001.5 Nissan Pathinder until 160k miles. It resulted in flashing CEL and then $1600 of coil packs and plugs. He still motors on now with 230,000 miles without issues of course not touching them.

 

[scurvy]

Originally Posted By: The Critic
...this is what happens when you run the plugs for twice the recommended interval:
(snip pictures)
Not too bad, IMO. Is it a good idea? I don't know, you tell me.

As long as the gaps are still in spec, looks fine to me. Probably good for 100k miles.

Originally Posted By: The Critic
New plugs were installed dry and torqued to 18.5 ft-lbs as per VW's specifications.

VW has all kinds of 'specifications' that make no sense in actual use. Lifetime fill ATF, anyone? It's true, it lasts the short lifetime of the transmission!

Before removal, the base of the threads always sees a shot of P'Blaster and I only use a 1/4" drive ratchet & socket. Spark plugs or glow plugs always go back in with a tiny dab of nickel-based anti-seize on the threads and a similar tiny dab of dielectric grease on the insulator where the boot goes. Otherwise next time they can and do squeak and groan and gall threads. Do I know better than the propellerheads in Wolfsburg? Depends on who you ask. I know what works for me...

Originally Posted By: 229
Ever check the price of the ignition coils? Makes plug replacement seem like a bargain. Just saying...


Ignition coil w/spark plug connector 07K905715F, $15.37 each.
Spark plug 'longlife' 101905600C, $11.71 each.

For a VW, this is pretty short money. Of course it's a better idea to not require replacements, and the spark plugs are cheaper than the coils.

Originally Posted By: The Critic
I replaced the plugs with a fresh set of NGK PZFR5Q-11. Why? Because NGK said this is now the proper plug, so perhaps there was an update. If anyone has any info on the differences between the J and the Q, I would be very interested in hearing it.


FWIW, VW now shows that part number as the appropriate one for the car. 101905600C has a remark listed in ETKA as "PZFR5Q-11 NGK".

 

[TFB1]

Originally Posted By: punisher
Agree, they don't look that bad to me. Whether or not the increased gap/voltage requirements will kill a coil faster is a valid question.


Very possibly, the coil(s) must build increased voltage as the gap opens and rounds off, less voltage is required for spark to jump from a point or sharp edge... Higher voltage can contribute to winding and/or insulating breakdown inside the coil...

 

[The Critic]

Originally Posted By: fdcg27
That plug looks pretty good.
How much had the gap grown over 80K?
You can still see the platinum button on the ground electrode and the center electrode still looks pretty good.
I wonder whether the 40K recommendation arose from concerns about difficulty in removing the plugs without damaging the threads in the head?


There has to be a reason for the factory recommendation, and I suspect it has something to do with the gap. Unfortunately I forgot to take a side-by-side with the new one, but in comparison with the new one, the center electrode has maybe 30% left.

I will measure the gap when/if I can find my tool, but compared to the new one, it was about 1.75x the amount IIRC.

But still, if they made 'em this far and the car ran fine, it can't be that bad!

 

[buster]

I'd like to know the gap difference as well. The theory about worn plugs impacting the life of the coils is interesting. 40k does seem short, but there has to be a reason they chose that interval.

IMO, it takes the average driver 3 years to hit 40k miles so replacing the plugs is well worth it. Relatively inexpensive to replace.

I use a tiny be of anti seize. I did not use use a trq wrench though.

I should have.

 

[PandaBear]

Originally Posted By: rjundi
My brother never changed them on his 2001.5 Nissan Pathinder until 160k miles. It resulted in flashing CEL and then $1600 of coil packs and plugs. He still motors on now with 230,000 miles without issues of course not touching them.


How can new plugs and coil cost $1600? I've only seen coil cost around $100-200 OEM and plugs up to $20 ea.

Normally I'd follow what manufacturer said but this is significantly out of what other manufacturer said on plug interval (i.e. 90-100k). It make sense to check and reuse if looks good.

 

[mechtech2]

The plugs look very good for not being touched for 80k.
Thanks to the double plat design, gap size is not increased much.
Any small increase might actually HELP with a bigger spark, BTW.

Good thing she didn't listen to your advice a while back.

 

[Vikas]

Nissan coil packs of that era had awful short lifetime. Most died within first 80K miles.

 

[229]

Increased current demands can also take out the coil drivers in the ECU computer. That computer is expensive and requires programming.