MJ, you know me from the M community...I wrote a how-to for the oil
That being said, yes, sometimes it's better to take an Infiniti to a Nissan dealer. For example, my Infiniti dealer wanted like $600 to change the spark plugs on my M56x. I took it to Nissan for $350. Normally, I'd do it myself, but the plugs by the firewall were impossible for me so I caved.