[welfare]

from what i've researched, this issue can often times be attributed to the close location of the pre-cats. apparently on start up the valve overlap allows tiny bits of the substrate to enter the cylinders through the exhaust. this causes severe wear to the rings and excessive cylinder taper. not just a problem with the 3.5, but also the 2.5 i4. makes transferring a used engine quite the gamble, since a lot of them out there have this problem.
i had this issue with my murano. luckily i found a very low k engine to swap in. deleted the cats for insurance. they had failed prior to this. which can also be a good indicator that this may be the cause of your oil consumption.