I've tried a variety of oils and brands over the years (Pennzoil, Castrol, Mobil 1, generic, Royal Purple, etc.) and have settled on Motul Econergy 5W30. It's a fully synthetic ester oil.
On my 2015 QX60, I used Royal Purple for the longest, giving a bit more pep that even my wife noticed after the first time I put it in, but, the engine was still what I call "chatty."
Ester oil is recommend for the VQ37VHR engines that are found in several other Infiniti models. Speaking to techs, reason being is the esters cause the VVEL system to not be so chatty, especially on cold start-up.
So, I used it in my Q40 (which I no longer have) and on my QX60. The result was a noticeably smoother running engine in both vehicles. The Q40, after full warm up, was so quiet at idle that you couldn't tell it was running unless you were standing next to it.
The only vehicles currently in the Infiniti lineup that require synthetic are the new turbo engines. Nothing else yet.
BTW, I became a firm believer in synthetic when I used to use it in my beat up 98 Sentra. Went to have the timing chains done as preventative maintenance (85k on the engine at the time) and the tech told me the inside of the engine was so clean, it looked almost new.
You definitely get what you pay for. Pops always told me: an ounce of prevention is worth a pound of cure.