Sorry, I know this subject keeps cropping up, but I checked the FAQ and did a search and couldn't find what I was looking for.

I seem to remember NGK being voted best plug, but there are several references for my car on their website.

TIA

 

I use the NGK Iridium plugs, never had any probs with them and they are rated highly in most fraternities

 

Thanks. I thought it was those, but there are two models on the NGK website (see link above): normal and 'laser', whatever that means. Supposed to be longlife, but are they worth the extra?

 

Quick answer: I've always found NGK to be the most reliable.

Cheers,

Languid

 

The NGK Iridium is about $12 while the NGK V-Power is $1.80.
Is there really ~8 x difference?

 

With the Iridium plugs you just need to make sure you get the right ones, the other type are for LPG converted engines

 

So which do I need for my non-LPG engine; normal iridium or laser longlife iridium?

 

I replaced my 2003 XKR plugs with NGK IFR5N10 Iridium. They were $12.00 a piece...no problems.

 

As cpm says NGK Iridium IFR5N10

 

Jaguar uses stock the IFR5N10, and according to jaguar should last 100Kmiles iirc (are yours already bad?). I always use the slightly cheaper Iridium IX version, BKR5EIX-11 (but then some heat ranges colder),:
New 4 NGK Iridium IX Spark Plugs BKR5EIX-11 / 5464 | eBay

 

What about for highly modified engines? Other than going a heat range colder. I remember reading where a tuner recommended the regular copper plugs instead the iridium ones because they worked better under high boost.

 

KenneBell has changed its recommendation from iridium’s to old style copper ones, they say that under high boost the copper ones hold up better:
http://www.kennebell.net/techinfo/general-info/SPARKPLUGS.pdf

Most of us do not run these high boost ranges, and I have no experienced issues (but I also haven't run these high pressures, nor have the capability to do back to back testing).

Am now experimenting with higher boost pressures (so above 20 psi), and have gone for race plugs for just to be sure, am using the Denso IK01-24 (these are still iridium’s).

 

The difference is strictly in durability. The V power plugs are the standard carbon steel electrode type that have been around for decades, while the Iridiums are, well iridium.

Standard plugs are good for 15-20K miles, iridiums are good for 100K+ miles. Several months ago I posted some pics of plugs that had gone over 300K miles and still looked like new.

Well worth the extra money IMHO.

 

I'm running the $4(?) NGK plugs and they work great...or, maybe it's the platinum ones. I know it's not the iridium. But they work fine. I did a lot of reading and asking, and I'm convinced that iridium isn't necessary for most applications.

 

The NGK UK site is unequivocal in recommending NGK IFR5N10 Iridium for both XK8 and XKR 4.2

NGK Partfinder for Cars & Light Commercial Vehicles

Whilst the change interval was different for the NA and SC 4.0 models, the 4.2 Jaguar Service Schedule lists 100k for both engines.

Graham

 

Thanks for your input, guys.

 

In mid-2017, this may be a little "dated" for discussion, but those of a certain age will recall that Denso/NGK "rescued" Jag electronics and by the looks of things, they are still doing a pretty good job. Just now, for the 5.0L 2010 XKR SC engine, PartsGeek shows NGK-94940 as recommended plug. Iridium wire and a bit "pricey" at $11.50 ea. $100 for 100k miles??? Not a bad trade-off, seems to me. As for BG engine FI/Induction cleaning, I ENDORSE it !!! Especially if you (or previous owner(s)) are/were "Geezers." Again, maybe $100-200 to know (and in my case, "experience") your engine "coughing up" part of a lung on test drive is worth it!!! (This applies to '03 XJR with almost 100k miles, 6% pulley and Mina exhaust.) The "Beast of the East" is STUPID fast, shutting down a "Rice Rocket" on I-20 at 130 mph. (The guy kept looking over at me from his crouch, with a "Who the Hell is THAT GEEZER???" look. He backed off at 130 and "sat up." Road victory to immateur Geezer! Comfy, sneaky fast, low-slung, Int'l award-winning design...it puts a smile on my face every time I light it up! EHT/SC

 

Clarification!! I can NOT find evidence (receipt) for DENSO/NGK plugs installed in my 2003 Jag XJR. Soooo, suggest you go to JagUSA/Denso/NGK for guidance. Adjust for your driving style/location. (Alaska heat range may be different from Florida.)
EHT/JCNA-SE

 

I expect a 2003 XJR is like my car: NGK IFR5N10