Used vs New replacement engine 2018 Pathfinder SL

Ever consider a Jasper remanufactured engine? I put in a Jasper reman in a 99 Pontiac and it ran and performed perfectly till the day I sold it.

As long as the good used engine comes with a warranty, I'd go that route. A new VQ35DD alone through Nissan is ~$12K, plus a good $2500 for labor and incidentals.

My sister bought a 2018 from a Toyota dealer and the oil had been changed only once, if at all. It had something like 38k.
It was taken to the actual Nissan dealer who discovered that is had been on a lease and had not been serviced.
They recommended a service where there is a series of three engine flushes as well as removing the valve covers and cleaning. It was not cheap.. She ended up paying over $1000. It seems to have done the trick since things are better.
However, both the remainder of the factory warranty and the extended warranty that she purchased were both rendered useless because the the abuse/neglect that the engine experienced.

Small block Chevy . Lol. I am keeping up on my oil changes on my 2016 as I hear there is a sludge problem.