Guess we just have to sit back and wait for Mafiosio's test run on the plugs

 

I have no doubt that there will be a 'difference' from one plug to the next and would be suspicious if there wasn't. Even if no changes were made to a car whatsoever and the owner simply did run after run after run, there would a be a variation in ET and trap speed. This is no different than the dyno runs in the above test.

How would those variation be factored out so that only the real deltas in performance remain? Since no two machines are identical, how would you know that the differences seen on one car would apply identically to another car?

This is similar to an amateur golfer claiming that one club is much better than another for distance after just a few swings.

 

Using a search engine will bring up thousands of random documents. Even if you had bothered to mention the search term in your initial assertion of authority.

If you knew what document you wanted to refer to, would being specific have been so hard?

The numbers have been presented as information worth thinking about. In particular the implications of running changes issued over time. There is no intent to get anyone to change their plugs any sooner or any later.

So, now the newest anomaly is the 100K miles that you state as being given by Jaguar and the 100k kilometers as given by NGK for the Iridium MAX which they position as their longest life Iridium type sparkplug. Looks like Jaguar and NGK ought to have a little talk.

 

Well, you know the answer to that.

Statistically significant data ... and all that.

 

....Hi Plumsauce, all the new Jags are equipped with NGK long lifes as standard OEM spark plugs. To my knowledge it was Denso plugs before and now its NGK's for Jags.

 

please keep on topic, and when you do, remember forums are great platforms for debate and enlightenment, not for food fights

 

Let me state my position again: I'm not interested in dyno runs. I appreciate that some are, but this thread is not about that.

I am very interested in the OP's plugs.

As a side issue I am interested in when to change my car's plugs. If jag had changed to other than 100K miles I would want to know but all the evidence is that jag have not changed.

My interest in deep issues of behaviour of spark plugs is minor. If I stumble on an interesting article and feel inclined to read it, I do. Keeping track of every article I read in a year is not for me of any interest at all. I do recall reading about Denso plugs, probably because I know they're in my car (and see above).

Anyone who really wants to know more has google etc and surely can look - or else they're more interested in argument than reading for themselves. For me, there's no debate because my parameters are the OP's plugs and my car. I won't be second-guessing jag as to which plugs to put in or when unless it becomes clear that using the OE plugs at the OE interval is a mistake.

It took me seconds to find an article that says Denso plugs should last over 200K miles: MOTOR Magazine Article | MOTOR Information Systems

 

Agreed!


Interesting article.

Back to the OP's plugs- it might be interesting to remove the deposits for a good look at the condition of the electrodes. In looking at the pictures, it appears that they're still in pretty good condition and might otherwise be suitable for continued service.

This still doesn't identify the root cause of the contamination. I also do not believe that this level is typical for the miles stated, or at any mileage for that matter.

Prior to buying the Jaaaaaaag, I owned an Infiniti J30 that was allowed to retire with 250,000 KM on it- and had the original plugs. I saw little sense in changing them as they looked the same as new ones each time I pulled them out. This is a car that sat outside 24/7/365 and was required to start in brutal Montreal winters with no block heater.

When my present S-type passes the 160,000KM mark in a few years I might pull the plugs purely out of interest's sake.