Been using HDEO Esso 0-30 syn oil in a 03 Altima and now a 05 Nissan X-trail. I trust this HDEO in my small QR25DE Nissan engines, it seems Nissan engines like a heavy oil as I have found in last 35 years driving Datsun/Nissan, many in here claim the same, their Nissans like heavy oil. I prefer the 0-30 syn oil for cold starts, a 10-30 to 15-40 dino is hard on gassers with smaller clearances on cold starts. Got caught other day with a 15-40 HDEO 50/50 summer summer blended oil in son's gasser car, there was a suprisiong 15F unexpected low overnight, the 3.1 chev rattled for 30 seconds, oil too thick, OC in straight 0-30 tonight.
In summer I actually run 3 litres 0-30 syn to one litre 15-40 dino both in XD3 HDEO because these Nissans run hot and like the heavy oil when warm in my experience, the blend really makes it run like a swiss clock on that blend, smooth and quiet, seems effortless. Would never use the 15-40 blend winter/or more than 0-30 in our harsh winters.
As far as the cat, no problems to date, my XD3 lable states "recommended for emmission controlled diesel engines", it is CI-4/SL, I dont know if that statement makes this oil easier on Cat or not, I hear the up coming HDEO rating of CJ-4/SM has less ads to protect the new cats on the new diesels.
I would go to a syn HDEO this winter, not dino and suggest a 0-30 HDEO which is close to a 40 weight gas rated but has the flow with syn base.
To note, your Nissan Manual probably says not to use syn oil, up here anyway, Nissan dealerships offer Mobil syn oil changes, they seem to have now accepted syn oil in their engines., I showed them the spec sheet on my XD3 0-30 HDEO and the Nissan mechanics started putting it there own Nissans at cost of half that of Mobil.
Cyprs