Just finished installing a low miles set of heads from an 1999 XK8 on my 2001 XKR (yes I plugged the VVT oil port).
However, I was not paying close enough attention and failed to notice the Jaguar Recommendation to use an antifreeze meeting WSS-M97B44-D specification on the coolant Resevour tank. Instead I asked the AutoParts Store attendant, who looked up the application for my 2001 Jaguar XKR in his Store's database, and sold me WSS-M97B51-A1 (Zerex G05).
The engine is now running, do I need to flush and change the out the new WSS-M97B51-A1 (Zerex G05), and Install the WSS-M97B44-D (Dexcool) ?
It is disturbing to see "Phosphate and Nitrate free" on these aftermarket coolants.
Thanks,
Mike

 

G-05 worked fine for me after a similar question 5 years ago. Hasn't seized up yet.

 

2nd to that the Zerex G-05 is what I used in my xkr and no problems in 5 months just don't forget to use distilled water

 

It is okay to use either one.

However, you cannot mix them.

If you did not do a complete and thorough flush, multiple times,
then you need to do so now, and pick one or the other.

I'm using the G-05, but did multiple flushes beforehand to get
rid of the previous Dexcool.