when my vx was using a lot of oil it was the pcv valve. I had put a new pcv valve in and used 2 qts in 1000 miles. got rid of the pcv valve by plugging the hose and putting a filter on the valve cover. went back to 1 qt every 3000 . with mobil 1 synthetic. there is no baffle in the valve cover and if the pcv valve sticks open it will suck oil and burn it . you will not notice it because the cat will burn it and no smoke will show in the exhaust. shawn