看看這個，的勤換油；

Is this a QX60 by chance with the VQ35DD engine? This engine was put into production starting in 2017 in the Nissan Pathfinde, Infinity QX60, etc.

If it is, this has got to be around 10 instances now where I've heard of this specific engine smoking like a chimney or sludged up to the point the only way to fix it is replace the engine. This is happening at low mileage as well, but I think 20K miles is the lowest I've read of yet. Most of the others were in the 30-50K mile range, but those folks at least did some oil/filter changes. If she indeed never changed or checked the engine oil in ~3yrs/20K miles, that engine, regardless of what it is, is probably toast.

I own a 2019 Pathfinder with this direct injected engine and I do know it blackens the engine oil quickly. I don't use the recommended 0w20 oil and I don't do 5000mi OCIs. I do them no later than 3500mi and I use 5w30 synthetic.