Since it seems like there are some new forum members who likely want to know about oil, here's the collective knowledge in this thread (I think; others can feel free to modify):
1. If you change your oil every 6k to 7.5k miles, any quality full synthetic will probably be okay.
2. Land Rover's original spec is really only achievable through the Gucci Castrol (available from your dealer, Atlantic British, and a few other places), and maybe Ravenol and Motul. An online search says that Mobil 1 Extended Performance can meet this spec, too, but there's been some debate.
3. If you go by the research that says the Land Rover spec has been superseded, then that opens up a few more oil options for you.
4. Supernerds like myself buy expensive oil (I use Motul) and change it every 6k to 7.5k miles regardless.
5. The original spec in the 5.0 engines at least was 5w-20. Land Rover now specs 0w-20 in its newer engines, and will use that oil if you take your LR4 into the dealer for an oil change. Most here (I think) still prefer to use the 5w-20.
If you are still under warranty and really worried about this, I bought my LR4 back in January 2016 with around 40k miles on it. It had a CPO warranty on it. I believe it had dealer service before then. I changed the oil every 6.5k miles or so with Mobil 1 EP. In December 2018 at around 80k miles, my CPO warranty covered the timing chain & guides replacement, and my dealer didn't question me at all on what oil I was using. Your experience may vary. Since then, however, I've been using Motul as I'm now on my dime for anything that goes wrong.