Hello all, I've been looking around this site for awhile but as you can imagine, it's hard to find a definitive answer on things when there are so many factors involved (price, make, model, opinion...) I bought a brand new 2010 Toyota Corolla XRS (5-spd manual, 2.4L I4) in June of 2011 and aside from the first two oil changes, I have been doing my own every 8-10k, full synthetic. The man. recommended oil is 0w-20 or 5w-20. Not sure what they used in the dealership/Mr. Lube, but I have been using Mobil 1 or Castrol 0w-20 for my own changes. For personal reasons, I would rather not use either of those brands, and I hear Amsoil is better anyway. So, after looking at the Amsoil website (there's even a warehouse in my city), I have narrowed it down to two choices: -0w-30 Signature Series Full Synthetic (AZO) -5w-20 Dominator Synthetic Racing Oil (RD20) About my driving.. I'm in the "big" city of Edmonton (1mil+) so there's a fairly balanced combination of highway/city driving. I drive my car pretty hard, getting it up to 210km/hr occasionally and frequently hitting 130-160 on the higway. Average highway cruise speed is 120-130, and in the city I still push it pretty hard. Winter temps drop to -40C (-40F) for at least 1 week every winter, and summers are mild and peak at about 30C (86F), lasting about 2 or 3 months if we're lucky So after typing all this out, it feels like I've answered my own question and will likely go with the 0w-30. I do still like my good mileage after all that abusive driving! Any thoughts? Input is much appreciated..