OEM spark plugs for 2000 S-type 4.0?

Could someone please advise me as to what are the OEM or preferred plugs to use for my 2000 S-Type 4.0 Jaguar? Thanks.

If you go to www.rockauto.com and your model and look under ignition you will find 29 choices of plug makers and materials. I think I chose iridium when I changed mine, and now I see they have ruthenium.

I used NGK PFR5G - 11E when I changed mine. According to the NGK plug selector there is a change point at March 2000. If before, they recommend PFR5G -13E. My car was built May 00. They were damn expensive but I guess they last 70k miles.