First here's the TSB in question: www.greenhybrid.com/discuss/attachments/f58/967d1228919408-winter-fuel-efficiency-toyota_tsb071002.pdf What do you guys think. Should I switch to a 20 weight oil for my 2AZ-FE engine? The part that confuses me is that the TSB first tells you to use what is recommended in your owners manual, but then lists which engines can switch down to a 20 grade oil, in which my engine is included. BTW my tC is a 2006 model year and the owners manual recommends 5W30. Thanks.