Good afternoon. I have checked the plugs today(which were all on the loose side) and looking at them wondering if at 100,000 miles these could be the original plugs. I have ordered a fresh set, but i do not know the torque setting. It would be much appreciated if someone could tell me the correct torque for the plugs. Many thanks. Anthony.

 

Your plugs likely have steel threads which are going into an aluminum head. When the engine heats up, the greater expansion rate of the aluminum precludes the need for extreme tightening.

the plug threads should have a very small schemer of anti-seize on them. Tighten them snug with the engine cold. Removal of the old plugs should also be done on a cold engine.

I believe the manual calls for 18- 22 ft lbs or 25-29 NM, with the larger number being for new plugs.

i would be extremely cautious going over 15 ft lbs. I tighten spark plugs by feel, and have never had one come loose or have the threads strip. Less torque is better when dealing with alloy heads and steel spark plug threads.

I’ve had to repair a few hundred heads that had stripped spark plug holes due to overtightening.


Z

 

I also tighten spark plugs by feel, being extra careful as I have a tendency to overtighten nuts and bolts. Been doing it that way since the late 1970s and have never had a spark plug issue as a result....

 

I also changed my plugs at 100,000 mile service. They looked so good that I wondered if it was necessary. I changed them anyway. Used on the right....

 

Me too.

That way you can feel any unusual resistance indicating possible thread damage in the head tapping and the 'bite' as the crush washer contacts.

Graham

 

One note on the application of anti-seize on spark plugs. If you are using NGK plugs, there is no need to use anti-seize on them, and in doing so, you are installing a "wet" plug, whereas the torque values in the service manual are for "dry" values. Installing it wet will result in an overtorqued plug. I suggest you check out the NGK web site for more information on this.

NGK has a new plug out, called Ruthium. They claim an improvement. Again, consult with their web page for the details. I changed to them recently, at the cost of $9.50 each from RockAuto. The normal NGK plug is around $6, so yes, this represents a HUGE difference, 50% increase (okay, it's $3 each). Still, it is WAY better than what the dealer will charge for these same standard plugs, upwards of $29.50 EACH.

 

I can’t bring myself to “dry” install a steel plug in an alloy head. Since I never use a torque wrench anyway to the factory recommended specification (on spark plug installs) I’m confident my “snug rating” is way below the factory spec. Knock on wood, no failures or loose plugs after 55+ years, a few decades of that as a professional tech.


Would you mind telling what tipped
you toward the new NGK Ruthium ? What improvement over their Iridium’s made the difference to you ? I read the NGK website info, but am curious about your decision process. Are you thinking they will last longer than the Iridium’s ?

Which NGK Ruthium is used for our cars ?

Did you get the DFE or PSPE electrode type ?


I installed the NGK laser iridium IFR5N-10 plugs about 17,600 miles ago, so I’m not
in the market for a new set quite yet, but would like to know what I’m missing out on.

The plugs I replaced had been in service for 100,000 miles, but looked fresh, by my rough standards.

Z

 

I read the propaganda on this web site NGKSparkPlugs. They claimed a slight improvement in combustion, etc. I don't put a lot of miles on my car, so this is probably the last set of plugs that she'll get while I own her. When I see that the dealer charges so much (up to $29.50 each), and I change them myself, thus saving a LOT of money over the dealer cost, I'm more willing to spend a little more money. I don't know that I'll see any real improvement in performance, but a slight increase in fuel economy is worth it.

The NGK Ruthenium plug is NGK 96457 . They are $8.56 each at RockAuto, plus postage. I try to combine my orders to reduce the impact of postage. You can find a 5% discount code searching the internet.

I am humored by looking at listings on BringATrailer.com at the XK8/XKR listings, where they sometimes post dealer service invoices. Changing spark plugs or transmission fluid for $700 is pretty funny to me. If I had to pay those prices, plus a 45 minute drive to my nearest Jaguar dealer, I wouldn't have this car.

 

100,000 miles is the recommended service life of sparking plugs for the Naturally Aspirated engine.
This is the form we filled out when servicing the cars 'back-in-the-day' at the dealer.

 

And they don't recommend ever changing the transmission, differential, or supercharger fluid, for what it's worth

 

This ^^^^^ x100

 

chiming in here...

i have three of these 4.2 SC jags....and multiple sets of plugs standing by for use.
i did buy a set of ruthenium's for TRAMP ('05 XJR 78k miles) currently on the stands getting multiple jobs done.
my train of thought is they should go well with the mina intake, pulley & exhaust...?...
i am very curious if anyone who has used them believes they have experienced any notable differences ?

many thx,

max, XKRFACE, TRAMP & Tres

 

I put them in, but didn't really see any difference in performance, but you have to be pushing an XKR HARD to see any potential HP gain. I'm hoping that I'll realize a fuel efficiency gain, but so many factors can affect that, it's difficult to measure in the real world.

 

I just changed the plugs in my Mercedes E550 from Iridium to Ruthenium. I was having sporadic problems with misfiring and decided to get a plug with higher ignitability. The Ruthenium plugs have a special triangular electrode tip on the grounding electrode that exposes the spark more than the iridium electrode does. When I changed the plugs, I could tell that the engine was smoother and it definitely stopped the misfiring. The E550 is the same performance level of the XKR so spark intensity matters. I will change the XKR plugs to Ruthenium when the time comes. One thing that was involved in this change was that I put the last set of plugs in by feel, which is usually what I do. When I removed them, they were way too loose, just about hand tight, which may have contributed to the misfire. I put the new ones in to 18 ft-lbs, which is what I should have done before, just too lazy to get the torque wrench.

 

Can't speak for the latter two but for sure they DO say to change the trans fluid - and have done for many years!!

Bit of a shortage of people who actually seem to read the tech stuff like that

 

Perhaps it would be more accurate to say that some of the transmissions were labeled from the factory as being filled “for life”. That directive did change as some point later on, but nevertheless it was wrong to say so at the beginning ..


Z

PS Giving the benefit of the doubt, I don’t want to assume your post was intended to be snarky, but it does have a unfriendly vibe to it, however unintentional.

Can’t we all just get along ? …. Rodney King

 

From the Jaguar workshop manual for the 2003 to 2006 XK8

Normal Maintenance Not necessary. Filled for life.
Severe Duty Maintenance Change the fluid at 48,000 km (30,000 miles) intervals.

 

pro·cliv·i·ty
/prōˈklivədē,prəˈklivədē/
noun

1. a tendency to choose or do something regularly; an inclination or predisposition toward a particular thing.
   "a proclivity for hard work"

Some do, some don't....

Honestly I wish I had more of an ability to gather, digest, put to use and store lots and lots of technical information. I'm getting better at it, with time, maybe. We all add what we add, and take what we take here. I'm a bit ashamed to say I've been more of a taker in the few short years, I hope to change that...

Seems the most AVAILABLE information for the regular dude is that they are sealed for life. Thankfully there are folks here who have been able to provide us with better and more current information 😊

 

Going a tad OT, but 'Severe Duty' encompasses more 'normal' driving conditions than the name implies. I've come across this on a few occasions. Here's one:

https://knowhow.napaonline.com/choos...l-severe-duty/

 

I believe we are driving in severe duty conditions all the time;

a) Hot
b) Dusty
c) stop and go traffic
d) short trips


I quality for 3 out of 4 of these “severe duty” conditions mentioned practically every time i get behind the wheel.


Z