The can recommend whatever they want. You can use whatever you want that meets the requirements.
Maintenance intervals, fluid recommendations..... hint hint lower cost of ownership
With some the issues that Nissan's OHC engines develop with some mileage and time, I would definitely use a full synthetic oil with 5k changes minimally twice a year.
Its never too soon to switch to synthetic.
As owner of a 1999 Nissan Maxima, 2005 Nissan Pathfinder V-6, and a 2008 Nissan Titan V-8, my son and I would be interested in learning just what OHC problems Nissan has had that might require synthetic oil to be restricted to a dino-like 5,000 mile OCI. My Pathfinder presently has 7600 miles on M1 10W30 HM, and has used about a third of a quart in this time. Oil looks very good. I'm doing a one year OCI, which should be almost exactly 10,000 miles.
Plenty of ticking, tapping, valvetrain, cam, chain, guide issues available in engines that aren't maintained. Most of the time, synthetic seems to be a preventative. I've abandoned Nissan already. My 1st 1/2 million miles were driven in a Nissan. Maybe 20 of them in the family over the years.
Btw, I could care less if your Nissans are perfect. I've seen too many that weren't.
Don't worry. The solution is Nissans 'ester unobtanium nano particle oil'.
A guy I knew put 120K on his titan pulling a 5,000+ trailer full of stage equipment for upcoming bands on tour. He did his changes at my shop and usually did 7,500 mile intervals on whatever synthetic 5w30 was on sale despite towing 90% of the time. He also brought his own PureOne filters.
His truck was totaled out one evening when a Semi-Truck slid out of control when traffic slowed and hit him while he was pulling a trailer. The truck was ruined, the roadie equipment toast, but he walked away.
He made a $50,000 settlement and now he runs his own business. Haven't seen him since.
He also had me flush the tranny with some Nissan Magic J [censored] that is $10 per quart at the dealer.