Spark plug readers wanted

[Darwin1138]

I read some time ago, that you can predict the future by looking the state of your used spark plugs. So, I ask to every professional spark plug reader out there, what do you see on my plugs?:
Am I going to meet someone special?
Do I need to terminate my current relationship?
Am I going to advance at work?
Should I sell my shares?
What are my lotto numbers?

Now, those professionals who don't have psychic powers, but have mechanical expertise, may need more data. In the following pictures are the spark plugs, with 20,000 km (12,500 mi) of use, that came out of a Peugeot 207 1.6 VTi. The spark plugs are Bosch Platin-Ir model ZQR8SI302 and to me they don't look worn out. The gap is between 0.035 in. and 0.040 in. altough I don't know the factory gap.

According to the warranty booklet, the spark plugs need to be replaced every 20,000 km (12,500 mi). I have changed them accordingly just to comply with the warranty, but I think that this is a very short interval, and I feel that I am throwing to the bin set after set of perfectly good spark plugs.

Why I ask?, and why do I feel that I know better than the manufacturer? First, this is a “Mexico only” service recommendation. In Europe, Peugeot establishes a 60,000 km (40,000 mi) change interval, and Mini specifies for the same engine a change interval of 160,000 km (100,000 mi).

One reason, could be the quality of the petrol that is offered in Mexico, but the fuel is imported from the US, it is a 95 RON petrol with no MMT, (this additive is famous for leaving deposits in the spark plugs and oxygen sensors), and if this was the reason you would expect that every manufacturer would do such a recommendation. In my previous car, a VW, the change interval was 60,000 km (40,000 mi) and one time I changed them until 80,000 km (50,000 mi) without any problem (no misfire, no increased fuel consumption, pass emission testing).

So, the only other reason that I could think of, is to line the dealership's pockets by performing unnecessary repairs.

I am thinking of leaving them for 60,000 km (40,000 mi), even though I will forfeit the warranty by about two months, but I have not had to make any repair under warranty, so it doesn't concern me too much. Is this a sensible idea? What are your thoughts and opinions about all of this?

Thanks in advance for your help.

 

[Papa Bear]

It looks like you are burning soft coal ...

 

[Boomer]

If there is no manganese add, then I would say the plugs look OK. You might want to consider going to a slightly hotter plug as they look to have some carbon on the porcelain but I do not consider this a big issue.

 

[SuzukiGoat]

A few things...that's a big gap. That electrical system is either ridiculously awesome, or they were improperly gapped from the factory.

The other thing I'm noticing is they look dark...reallly dark. Either you NEVER idle the vehicle, or they needed to be changed sooner.

And finally, while the stained porcelain has zero effect on the plugs ability to do its job, it hints at an ever so slightly mistorqued valve cover. Have the dealer check it, or do it yourself...not hard.

 

[Tegger]

Am I the only one who is astonished by the very heavy corona-staining on the porcelain? I would NOT expect that after a mere 12,500 miles.

And the electrodes look brand-new, with no erosion visible. I wonder if that 12,500 mile change interval is for NON-platinum/iridium plugs...

 

[SuzukiGoat]

Nope, me too, I suppose the plug could be mistorqued as well...but I vote the spark plug seals on the valve cover are leaking an infinitesimally small amount of oil.

 

[Roadkingnc]

The purplish stain in the porcelain is caused by fuel additives. The plugs themselves look fine and I would run them for at least 60k if not more.

 

[spasm3]

Is it just me , or do they look like one heat range too cold?

 

[Bluestream]

Running Rich IMO

 

[punisher]

Reading, or trying to read spark plugs, on a street car is next to pointless. You can get general ideas, but nothing specific.

At the track you have the plug wizards from NGK, Champion, Denso etc, and these guys do nothing but look at plug electrodes through magnifiers all day long. You supply them with specifics (engine specs, fuel specs)and even then sometimes they give back erroneous info.

Reading plugs on a street car, burning any number of unknown fuel combos/additives at 7,000+ ft altitude is magic fortunetelling tea leaf reading stuff, and may have the same chance of being correct.

 

[circuitsmith]

The center insulators look too dark to me.
This could be caused by a weak spark. Maybe because the gaps are too big?
Are these OEM type plugs? That's all I would use.

 

[Clevy]

There was an old timer at the track that would run 1 lap,pull the plugs and adjust the air/fuel based on how the plugs looked.
No iridium plugs or platinums either. He was pretty amazing. Anyone with a carb could pick up time with his tuning.

 

[Darwin1138]

Hey, thanks to all for your comments. I searched for more information about this and I found this page where they recommend that in the THP engine (Turbo High Pressure) the change interval should be reduced to 20,000 km from the 30,000 km that Peugeot recommends because of the high temperatures induced by the turbo. But they don’t say anything about the non turbo engine.

The official gap is 0.75 mm (0.030 in.) and they say that when the gap reaches 0.95 mm (0.038 in) you could get performance issues. I measure the gap in 0.035 in, so now I think I have a parameter, I will measure the gap at 20,000 then at 30,000 and see how much it changes, if the gap gets over 0.040 before the 30,000 km, then the manufacturer could be right, but then again why in Europe they specify 60,000 km?

Now, Tegger mentioned that maybe the interval was for non iridium plugs, and that got me thinking that the 206 and the 307 use copper plugs, and the 207 GTI, the 308 and the 508 use the THP engine so the change interval of the Peugeot range would look something like this:

206 20K
307 20K
207 60K
207 GTi 30K
308 30K
508 30K

So I imagine that the people in the upper management were looking at this table and then someone said:

-"Well, that is just too complicated mate!!!, Why can't we just make the same interval for everyone?"

Then other person said: - "Ohh yeah!! let's make 20k for everyone, that's much easier to remember!!! plus we can end this meeting earlier and go to the pub and watch the game!!!"

And all in unison said: "Yaayyy!!!!!!" 20K!!! Mexico!!!Mexico!!!Mexico!!!

Anyway, I think the plan is to inspect the plugs every 10k or 20k to see how far can I push the change interval.

Finally, I will inspect over the weekend the valve cover to see if it is leaking oil as SuzukiGoat and Tegger suggested.