Can you use Royal Purple ATF Max in a 2002 x-type to replace the ATF IDEMITSU K17 (Jatco 3100 PL085) oil in the transmission? Thanks to anyone that can help with this in advance.

Does it meet the Jaguar spec?

If your car is out of warranty then you can take the gamble. I found that if you call any oil manufacturer they will all claim that there is a fluid that meets the spec after all they are trying to make money.

But if you are looking for a cheaper alternative:

jaghelp.com: Jaguar X-type recomended fluids

Best of luck!