I was horrified to discover the breather tube on my 97 3.1 Monte Carlo which runs from the throttle body area to the rear valve cover was accidentally disconnected by me when I changed the air filter last year. This rear valve cover is nearly invisible and I guess I am lucky I ever saw it. I have run Trop Artic 5-30 and Pure One every 3K since new and now have 71k on the car. I don't have a consumption problem. I never go down dirt roads. I am waiting an oil analyis from Blackstone and will share my Si findings with you.