The evidence is the sheer volume of owners that follow the OEM schedule with no ill effect. Do you know of owners that suffered problems by following the recommended interval?

 

Both the original and revised new maintenance schedules are 100K miles for the V8 plugs. You're the only person I've ever seen say to use 30K.
Actally they don't say that. GTR (TOPIx) goes into detail. Let's stick to spark plugs.
100K. It's consistent with both jag and Denso recommendations and there are technical articles about why. Please post your detailed evidence (not opinion) about why.

 

first its hard to foul IR and platinums compared to conventional, they last longer and much less prone to fouling in my experiance. Also I think you getting too worried needlessly at this point. Change the plugs, run them for 10k miles and pull them out and look again. Yes theres some oil(more normal for SC/Turbo cars) and ash deposits. Yes there alot of crap added and taken out of todays gas in addition to gas samples Ive seen with over 10% ethanol. Keep your oil changed regularly, run supreme on SC engines and have alook in 10k and THEN see what you have on the fresh plugs.
As for your cats, normally missfires/rich mixes are what take them out prematurely. Not octane or gas issues that Ive seen...

 

Did you not get the bit where the Jaguar recommendation is different for North American markets on the same engine, on the same plugs, running the same grade of gas?

It was brought up as worth noting. In addition, some reasons for the difference were proposed.

No where was reader *told* that they *must* do anything different from whatever turns their crank. If anyone wants to run try to run their plugs to 1,000,000 miles they are free to do so. If they want to use Krazy Glue instead of anti-seize, they are free to do so.

If everyone *must* do as their Jaguar marketing organisation tells them, then US owners *must* change plugs at 100,000 miles and UK owners *must* change plugs at 30,000 miles. Same engine, same plugs, same gas.

The question then becomes why are the recommendations different and whether US or UK(+ROW) owners are better served.

So you keep on saying, but without posting the citations.


I am not the one claiming that there is "detailed evidence". What I *have* done is cited the original Jaguar spec and suggested that there ought to be a reason behind the difference.

 

Where was it suggested that an owner would suffer problems?

That is not what was said.

What was said is that there is an interesting anomaly in a Jaguar publication.

What was also said or at least implied is that an adequate spark may not be a satisfactory spark for a particular owner or purpose.

Given what you know, how many hours of engine time does the FAA or DOT allow for plugs in piston engine planes? The interesting thing about planes is that pulling over to the shoulder and waiting for a tow truck is usually not a good option.

 

I think we've heard all sides of this, there's plenty of information to consider, and like oil change intervals, spark plug changes should be placed up there with it, although I think the types of plugs can have a little more science involved in their support or opposition.

There are many opinions, and logical arguments for the various debates, and sharing them with the respect for all others, is what we all need. Thank you guys for your input...take a deep breath, and exhale. Feels better, doesn't it.

 

For the OP- has there been any unexplained loss of coolant? I've got 5 or 6 engine geek buddies following this thread, this is one of the suggested causes for the weird deposits.

For plumsauce-

Neither the FAA nor Transport Canada (not DOT) sets any replacement interval for components. That's a common misconception, but is not how the industry works. The OEM develops the interval based on solid engineering and testing principles using well established procedures and methods. The OEM presents the equivalent of a thesis to the regulatory agency in their home country for examination and approval. Once an initial basic interval is set, field data is used to confirm that the interval is appropriate or possibly can be extended.

I know that the auto industry does not certify products to the same standards via the same methods but the feedback loop with respect to reliability and durability is still there.

I was always amazed by owners who 'knew better' than the OEM with respect to the above and would farque things up royally and then submit a warranty claim hoping that we would pay. Again, this is getting way off topic. If you're interested in pursuing the discussion, maybe start a new thread?

 

The newer schedules on GTR/TOPIx are all 100K including for NA markets.
I never said that. Not much point ranting about something I didn't say.
The newer stuff is NOT different.
FFS. If you want to read it do some googling for Denso iridium spark plugs.
It appears that the ONLY place it says it is something YOU found. And it's out of date, if it indeed says what you claim.
Maybe you found a bug.

 

Thats 1 of the things I thought too at first. But I know another nice thing (IMO) about the red Jaguar long life coolant is its ability to stain, and that includes the electrode when coolant is in the chamber and burned even in small amounts. Ive seen this on Jags and most notably on my Frontier when i had a small leak in the after cooler under the blower. (Yes I run Jag coolant in a Nissan I was loosing small amounts and when I pulled the plugs they had light pink tint to the electrodes. So if he's running red coolant I looked at the plugs and didnt see any evedince of coolant which is why I didnt mention that.

 

Wow, that's worth knowing! Thanks.

 

...Hey Mikey no loss of coolant, only thing I have to put in half a quart of oil every 3 or 4 months depending on how hard I drive the STR. I would like to say thank you for everyones opinions and facts on this issue and I appreciate the interest you all have taken to investigate it.

Cheers!

 

I have just been on the phone to the tech dept. at NGK here in AUS.
They told me the plugs that last 100,000km are the 'double iridium' type not the single iridium ones; BKR5EIX11 being single iridium IX. The single ones have a recommended interval of 'only' 60,000km.
Also NGK do a slightly lesser plug; a 'OE Laser Iridium" to fit the STR.
I am not sure if there if there is a 'double iridium' to suit the STR.
AND I am not sure if the original JAGUAR branded plugs (C2A1535) are really one of the above NGKs with just Jaguar written on the plug.

Anyhow due to a deteriorating poor idle, I had to change all the eight points. The condition was so bad the engine was nearly stalling; at idle (in gear). Also with poor take of.
Probably not all points would have needed changing but the dealer never changes just one or two, all 8 are usually changed.
I was also told by the dealer to change all the plugs as well, as bad points usually foul the plugs! Even though these plugs had done nowhere near 60,000km.
Odometer reading on vehicle: 68,000km.

 

The way they put it on the NGK Japan site is: "The Iridium MAX plug lasts even longer than a platinum plug with a life of 100,000 kilometers !!"

The construction of the NGK Iridium MAX is iridium center electrode with a platinum side electrode carrying a small iridium inlay. The part numbers are suffixed with "P" to differentiate from the NGK Iridium IX.

The NGK Iridium IX is what is generally available in North America.


100,000 kilometers = 62,137.12 statute miles

 

The correspondent who alludes to the existence of authoritative material to buttress a case is generally the one who ought to supply the citation.

The citation was supplied by name.

 

The only one that really matters is Jaguar's. They state 100K miles.

I told you to google for Denso iridium spark plugs. Is that really so hard. No.
It's years out of date and has been superseded.

 

Looks like there has been a dyno test done comparing denso iridums vs. NGk iridiums and pulstar. YOu be the judge which is better, have a look, http://www.sparkplugs.com/sparkplug4...fid=0&KID=3147

 

If I had that car and wanted to do good dyno runs I might be swayed by that article, but I have an STR and will likely do hardly any or no dynos. YMMV.

 

Anybody that's ever operated a dyno would recognize those variations as typical scatter. There's typically more difference from one run to another on the same plug than there is from the worst to the best plug.

A spark is a spark.

 

UMMM not really, some spark plugs are designed to run hot others cold for the same vehicle. A spark is a spark may be true on a flint and a rock but not plugs.

 

Yet amazingly, no evidence can ever be provided of such things.

I think you've misunderstood what 'hot' and 'cold' plugs are for.