First of all, find out if your engine has already been replaced. The XK came with a Nikasil issue that caused catastrophic engine damage. Do a small search on Yahoo with two words: Nikasil and Jaguar. You'll see the results.

As for fluids, it's far too varied an issue to give a good recommendation. I personally use Penzoil Platinum 20W50 but I have over 100K miles. I'd also change the tranny fluid, since it's probably never been changed, and if I'm not mistaken it's Mercon V ATF.

Chips and mods are few, but specifically the chip. Very expensive and only Arden sales it. There are lightweight pulleys and exhaust systems that mke the car run bit better, but it's a Jag man. Everything is expensive and not too efficient. I love the sound of a Borla on the Jaguar's V8...SEXY!

Search though, because the Nikasil issue can bite you hard in the buttocks. BTW, WELCOME

 

Welcome !
I use Castrol .In fact other brands are good as well . Just make sure you do use the correct viscosity when fillin her up . Still, most owners say you can use 5W30 instead of 10 W30 or vice versa .

 

Car fax...and there is a site associated with Jaguarcars.com that has some info as well. I'll post that link later.