Sorry... can't figure out how to post the PDF or the TSB .... A Toyota Tech Service Bulletin # EG018-06 issued on March 29, 2006, indicates that ILSAC GF-4 , 5W20 or 0W20 may be used in a variety of modern Toyota engines that used a heavier oil. The list includes the "MZ" series engine (3MZ-FE) 3.3L V6 in my Sienna. Originally, it called for a 5W-30. I've been using 0W-30 for years and I'm wondering if I can safely 'down grade' to a 5W20? Any thoughts??