XJR spark plugs

[CHJ]

I see on the Jaguar servicing schedule (2001MY on) the recommended service life of the XJR spark plugs is 30k miles, but its 70k miles for the non-supercharged engines. Are they the same plugs but the shorter life is due to the extra load?

30k miles seems quite a lot in any event, let alone 70k miles. What do you think?

Thanks, Chris

[Jaguar steve]

I've changed a few sets on the V8s. The ones I removed were obviously old - the insulator bodies were dirty and discoloured and some of them had partially siezed in the heads - but all of them still had close to the origional gaps and hardly looked as if they needed changing.

I guess it's a combination of modern engine managment giving a much better controlled and cleaner burn, developments in fuels and the use of Platinium tipped plugs that all help to give such a long life.

I remember changing plugs every 10000 miles as part of a major service not all that long ago, and somtimes finding that a set had lost performance and not even lasted that long when the car was plugged into diagnostics.

I'm guessing why an Rs plugs are on the service schedule more often is the assumption that the R would be spending a lot of time at much higher revs so at 30000 miles the Rs plugs may have fired more times than a 8s at 60000 miles.

[CHJ]

Thanks Steve.

I'll think I'll change mine since I suspect they will have done at least 30k now.

[Jaguar steve]

Shop around for plugs - you'll get robbed otherwise.