I was told by my local Jag shop to only use the "genuine" spark plug (Champion); and then to only use the ones manufactured in the UK, which they, coincidentally, had in stock.
This sounds a bit fishy to me.
Does anyone have any stories regarding spark plug (good or bad results) they'd like to share?
Richard, I have run into owners of XJ40s who claim to have had problems with plugs other than the Champions specified by Jaguar. The problem with any confirmation on something like this is, of course, the human error factor as to whether the proper heat range was purchased or the proper gap set on the plugs.
You can use the standard plugs listed in the owner's manual which are Champion RC9YC (RC9YCC in the UK) for the 3.6 litre and 4.0 litre versions. Gap is 0.035" (0.9mm) The 3.2 litre motor uses the Champion RC12YC lug -- same gap.
Personally, I am using Bosch Platinum in my 3.6 litre and have for
50,000 miles with no problems. The only reason I use those is because the parts store had a special on them!!
If you have concerns, simply use the Champions available at any parts store for a couple of bucks apiece.
I have not used Champion spark plugs for decades. My motorcycles did not perform well with them. Also I have had more Champion stick in the heads and gall the threads or worse. Perhaps they have improved but the plugs I use now have never let me down.
I use nothing but NGK/ND plugs. Oh alright, I use Bosch too when NGK is not available.
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I laughed when I see these specialty plugs appear - "New, four earth grounds or split grounds." NGK has made those for many decades, in fact you can buy full earth grounds (Carbon foul-less) if you wanted. Platinum? Tss NGK makes iridium!
I am not discounting other peoples experience, I am only speaking of mine.
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