Nissans have the steel time chain good for 200K miles, I will not use a 40 weight on a newer Nissan but I use a HDEO 0-30 CI-4/SL syn, it is a very heavy 30. There are many concerned on timing chain lubrication, the Japanese have been concerned with the thinner new oils now and chain lube. Also, a Nissan does not make as tight clearances as say a Honda requiring 20 weight oils. I have driven Nissan/Datsun for 28 years now, they do great on heavier oil, as they age to 300K I use 40 weight in them.
For example, in my manual for my 05 QR25DE 4 cylinder, Nissan will allow me to use a 10-40 oil in temp range from 0F and up, that is a thick oil for winter in a four banger, and Nissan usually shows preference to dino oils too, I always use syn oil in them, no problem. 5-30 is generally
the perfered all temp oil for Nissan.
Cyprs