Kind of funny that this topic should come up. I just changed the oil on my 91 Nissan Pathfinder with 180,000 miles from M1 10w-30 to 0w-40 the last change. I have never had a problem with the 10w-30 and the truck doesn't burn any but I wanted to have one less oil weight around. Unexpectedly, the 0w-40 made the engine quieter and smoother, especially at idle. I was really shocked. Maybe the heavier oils dampens sound and vibration better.
Cary
Cary