I ran into a similar problem on my wifes 2005 altima.we purchased car new in fall of 04.I have always used dino oil. Our car would burn about 1 quart every 5000 miles .it wasnt a great amount so i thought nothing of it.
Last fall I let a parts store saleman convince that because of the mileage on my car(146000) I should switch to a synthetic brand designed for engines with high mileage.With the synthetic oil comsumption more than doubled.
After switching back to dino based oil my usage went back to what it previously was.
On my 460 I use 15w-40 rotella on while I have some usage it's very minor.try switching to regular motor oil and see if it helps your problem