I'm planning on replacing my spark plugs with NGK Iridiums at my 90,000k service, and while trying to find the part number on the NGK website, I found that the plugs they recommend for a normal TJ are different to a Ralliart, including the Iridiums.

For a normal TJ they recommend BKR5E-11 for the front bank and PFR5J-11 for the rear, with the Iridium replacement being BKR5EIX-11 for both banks.

In the Ralliart they recommend BKR6E-11 for the front and PFR6J-11 for the rear, with the Iridium replacement being BKR6EIX-11 for both banks.

Obviously the part numbers are fairly close, and I'm guessing either would fit, but does anyone know what the difference is with the ralliart ones? I would understand if they had better plugs as standard, but I would have expected the Iridiums to be the same. What's the difference?

I noticed this the other day when going through the magna car manual......

Ralliart 3.5L engine and 3.0L engine share the same spark plugs.

All non-ralliart 3.5L's use different ones.

..............different temperature plug maybe...?

It could only be temperature, as they are the same thread and same size plugs from what I can gather.

Either or would work, I would buy whichever are the cheapest :D

EDIT: Iridiums are not worth the extra money IMHO. The only reason people notice power gains when fitting is because they are going from a cruddy old burnt out plug to a new plug, nothing to do with the fancyness of the plug. Iridiums are designed to last longer and have higher melting temps than copper plugs, but in a regular motor its not needed as the STD units are already more than enough. Your better off changing the plugs twice as often with NGK or Bosch entry level plugs than you are to buy iridium units and leave them in for ages. And you will still end up with more money in your pocket as a set of NGK/Bosch plugs are $24 vs $75 odd.

I have tried both plugs and even on a high boost/heat motor I have no dramas running regular (dare I say cheap) plugs.

Yeah but with the Iridiums I may be able to lean out the mix a bit too (Unichip). I was considering a retune anyway, as I don't think it's as good as it could be. Too late now anyway, I just bought them. $108 for 6 at Supercheap.

dont the iridium only last about 40-50,000k's where as the platinum last around 90-100,000k's?

Yeah but with the Iridiums I may be able to lean out the mix a bit too (Unichip). I was considering a retune anyway, as I don't think it's as good as it could be. Too late now anyway, I just bought them. $108 for 6 at Supercheap.

Although they couldn't hurt, your std copper plug would still be well within its temp range for a NA running a fairly lean mixutre at the top end of the load/rpm range.

Does anyone have a service interval for spark plugs on 3rd gens? I was under the impression they were 60,000 on the rear bank and 30,000 on the front bank.

Does anyone have a service interval for spark plugs on 3rd gens? I was under the impression they were 60,000 on the rear bank and 30,000 on the front bank.
nah, 90-100k on the platinums (same service as belt) & 45k for the front bank.

im to understand that there are 2 kinds of iridium plugs .6mm and .8mm ix type is only good for 60k but the other is good for 100k.. i suppose a trip to ngk.com or what ever would clear this up.... instead of ppl like me thinking things, that are proably wrong


*edit*
Type Service Life Benefits
Nickel Alloy 20,000 - 40,000 kms Standard style of spark Plug.
Nickel Alloy
(V-Groove) 20,000 - 40,000 kms Improved ignitability due to sparking at periphery of the electrode.
Platinum 0.8 mm dia. 100,000 kms Long service life and even better ignitability due to a small diameter centre electrode
Iridium 0.8 mm dia. 160,000 kms Extremely long service life. Same level of ignitability 0.8 mm dia. Platinum
Iridium IX 0.6 mm dia. 60,000 kms Long service life. Same as 0.8 mm dia. of Platinum and extremely good ignitability characteristics. (Better than 0.8 mm dia. platinum or 0.8 mm dia. iridium)

*edit*
gee im good

Yeah I got Iridium IX's. Should be good for a 12 second quarter now.:D
Only the best for my boy! 60,000k's is pretty good. We'll see if it makes a difference. It'll be hard to tell, cos they're going in with a major service, so it'll probably feel better regardless. Hard to know if it's the plugs. Oh well, some sucka's gotta buy em.

pretty sure, the higher the number in the part number the longer the reach or heat path...

i could be wrong, i used to sleeep thru tafe sometimes

Ralliart and 3.0 litre plugs are one heat range colder. That is the only difference (required due to the compression of the engines)

Cheers
Heath Young