Upon asking Nissan if they allow the use of synthetic oil on the Xtrail, they replied only if you use their synth oil- Nissyn 15w40 by Conoco. Well, i checked out this so-called synth oil which costs P2360/4L at the dealer. It's rated for both diesel and gas, API CI/SL.
This is very, very similar to Conoco's hydroclear Power-D 15w40, which carries the same Api rating, a hydrocracked mineral oil which is marketed as an alternative to synth oil. It's not a synth oil rather a higher quality mineral oil.
If its the same oil, just re-branded by nissan, then it's not worth P590/L- you can buy hydroclear power-D 15w40 at P850/4L or P212/L.