I just purchased a 2012 4Runner V6 and would like to use premium oil in the motor. I have looked at Royal Purple, Redline, and Amsoil but don't know which is going to be the best for the engine that I have.
Most any synthetic will work just fine. Personally I run AMSOIL as the local re-seller gives me some great deals that the auto parts stores can't match.
If you want to get technical start reading BobIsTheOilGuy.com forums which has tons of info on every fluid for your vehicle.
Toyota's 0w-20 synthetic is actually a very well regarded oil, and it's cheaper by the case at your parts dept. (not cheaper than Mobil 1, however, but less expensive than by the quart.)