Toyota P/N C0009-00W20-12 This one liter bottle Toyota brand 0w20 sells for under $6 at the Toyota dealer parts department. The bottle does not specify whether it is synthetic, full or blended synthetic. However, their computer is showing synthetic in their description. The price is telling me that it is probably not synthetic. I searched another forum and someone is saying the above is made by ESSO (Imperial Oil Canada) for Toyota with special additive. Adding to the confusion is that a Toyota Prius Product Marketing in the US posting message below: "We know there's been much discussion over the new synthetic oil guidelines from Toyota. As was mentioned back in April, the new oil will eventually roll out across more lines and manufacturers and provide lower emissions and improved fuel efficiency. The owner's manual lists the use of 0W-20 and 5K oil change intervals so we can't really comment further on what would void your warranty. The synthetic oil should now be available at all dealers and should very soon be available in bulk, which will reduce the costs for everyone. Genuine Toyota Motor Oil 0W-20 contains a Toyota specific additive package within it, making it not interchangeable with other synthetic oils of the same weight such as Mobil 1. We can't say much more now, but stay tuned for more info shortly, our experts are doing their best to provide more information as it becomes available. Best, Erica G, Prius Product Marketing, TMS, USA " Should I go with the Toyota unknown/synthetic oil, or should I use major brands 0w20 full synthetic like Quaker State, Castrol, etc?