Toyota doesn't really have their own spec, like GM has dexos, Ford has WSS-M2C930-A, etc... Toyota says use API approved SN oil in the recommended grade. That's their spec. I've been using SynPower or NextGen SynPower for the last 50K miles in a Toyota Camry, Lexus GS and Lexus SC.
I know that for the 2AR-FE engine Toyota says using conventional will get you 5K miles and synthetic will get you 10K miles. (You'll have to manually reset the oil change reminder light midway, which is what I do). That's all the specifics they give. Despite Valvoline not being a long-drain oil, works fine. I've done a few used oil analysis, TBN is shot at the end of 10K, as one would expect, but other than that it's fine. I mean you're throwing the oil out anyway, is having a TBN of 4.5 remaining after 10K miles really valuable?